I didn't see that anywhere in the doc's I saw; was more like a 1:2 kill ration for Ukraine, or at least a general casualty exchange rate of that sort. Definitely didn't see any 7:1 ratio for anything in it.
I think part of it is Ukraine is able to save a lot of their wounded and get some of them back in action thanks to western medical tech, where as most wounded Russian's expire or are permanently disabled when wounded.
The only way I believe the 7:1 is if Ukrainian civie casualties are added it; then I could see it being 7:1, because of how many strikes on civie targets the Russians have carried out.
Yeah, this.
If Ukraine was actually losing troops at a 7:1 ration to Russia, Russia wouldn't be struggling like they have been shown.