I am not disputing that number, but could you support it with a citation?
What are the actual numbers of killed and wounded on both sides? It's difficult to wade through the numbers being thrown about.
Only those doing the fighting are giving figures - and true confirmatory studies or facts simply do not exist. I'm not publishing an academic article, only trying to make a reasonable guess for a social-media board. My method:
The first question is: what's the ratio of killed to wounded? A "rule of thumb" figure is 1:3. It may be higher or lower
For example, the Donets Peoples Republic (DPR) reported as of 26 May, 2022 that they had 1,912 soldiers killed and 7,919 wounded (a 1:4.14 killed-wounded ratio). Zelensky gave figures last year indicating Ukraine's was a 1:5 ratio.
You can Google these yourself and decide who you trust.
Regarding total killed:
the Head of the EU in November said "100K Ukraine Military Officers have been killed." We assume she means soldiers (she also mentioned 20K civilians). The Russians claim Ukraine KIA is twice that number. The Ukrainians (and FR posters) claim the exact same thing about the Russians.
Again, whose figures do you trust? But most sources are saying KIA on both sides is 100K or more. What do you think is possible - given 1000-mile front, at least 750K men fighting directly, and the greatest expenditure of artillery since WWII?
We can only make an educated guess.
400k is plausible if one includes wounds like John Kerry’s in Vietnam. ;-)