They claim that many killed. Generally speaking the ratio of wounded to killed is about 3:1. If that’s the case here then you’re getting close to 10% casualties within a couple of days - that’s unsustainable levels of loss. Not to mention presumably a good portion of the 190,000 are support troops and not combat so for the actual combat units the ratio would be higher.
Again, this is all based on estimates you should take with a boulder of salt but if they actually have suffered 3,500 killed so far things are going very, very badly for Russia.