OK I see it, but still do not know how it got there
Ah, never mind.

It looks good, BTW.
Back on topic:
Approximately 3 million non-Jewish poles died under Nazi occupation, add another 3 million Jewish poles and you have about 20% of the pre-war population dead. The population did not get back to 1939 levels until the 1970's. Poland was under Stalin longer than it was under Hitler, and nowhere near that number of people were killed by the regime.
I'm not sure how these things are calculated. For one thing, IIRC 6 million was the
total loss according to some estimates (others go even up to 8 million) - meaning simply the number of people who did not survive the war on
both sides of the Russo-German "border". But I might be wrong (I can't check my books now, my daughter is sleeping).
According to the book I have at hand, during the first two years of Soviet rule on Polish soil, more than 1 million people were "repressed" - shot, imprisoned, sent to labor camps etc. At least 30 thousand were shot to death, and around 100 thousand died in the camps. We should also take into account the great number that never returned simply because they had no means or weren't allowed to travel (it's a long way from Kamchatka).
There's also the problem of "fluid" borders: how do you calculate the change in population of a country which has been "moved" on the map? And what was the actual
percentage of the population killed (in each of the parts)?
Last but certainly not least is Stalin's sly strategy evident in his handling of the Warsaw Uprising: Russian troops did not kill those Poles. But it can be argued that those people were killed on Stalin's order. But then, of course, you could similarly say the massacres in Volhynia were indirectly led by the Germans (well, more than that: there are reports of the Germans supplying both sides with weapons...).
Also worth remembering is that the NKVD was killing Poles well before WWII. These were Poles living within the Soviet Union, of course - even after the repatriations which were a consequence of the Riga Peace Treaty there were roughly 1.1-1.2 million Poles living there. Of these several hundred were killed in the "spy hunts" of the 1920s. There were also many Polish victims of the Great Purge. But that's all probably beside the point.
Finally, I'm a bit concerned about this method of comparing body counts. Isn't it a bit insensitive? (There's that poem by Szymborska about counting deaths by the million.) Both the Russians and Germans killed civilians and prisoners of war. They did this on a massive scale. Yes, perhaps Stalin left less casualties in Poland than Hitler did. But just think of Holodomor - this happened in a land that was once a part of Poland. It did not happen to the Polish nation but to one closely connected with it historically. That's 3 to 5 million dead within two years!!! I'm not sure that could be called a lesser evil. Could the same thing have happened in Poland (in later years)? Who knows?
But you're generally right: Hitler's plan was to exterminate the entire nation (Poles happened to be the only one of the occupied nations that could not enlist in the German army), while Stalin's was... I'm not sure what exactly. Probably to conquer all of Europe, and then the world. But for the time being it might have been "only" to get rid of the "cream" of Polish society.But you're generally right: in Poland, Hitler seems to have gotten much farther down the extermination path. I'm not sure if he actually wanted to kill all the Poles to the last one but whatever he had in store for them certainly couldn't have been pleasant (BTW, Poles happened to be the only of the occupied nations that could not enlist in the German army). Stalin's plan, OTOH, was... I'm not sure what exactly. Probably to conquer all of Europe, and then the world. But for the time being it might have been "only" to get rid of the "cream" of Polish society. Though, IIRC, Stalin and Hitler were both Poland-haters, and considering Stalin's success in exterminating some other nations.......
Still, re Florestan's suggestion, I'm sure most Poles would much rather remain in the British "domain". However, during the Tehran conference Stalin managed to secure that prerogative, and apparently without much difficulty.

[EDIT: major changes in penultimate paragraph - I've left the previous version (crossed out) for those who want to check]