Journalists and think tanks are tracking the war in Ukraine with varying degrees of expertise. In addition to open-source intelligence (watching the press and social media and trying to validate items) and commercial satellite imagery, they are using the press releases of various governments.
This leads to things like the ISW quoting the WSJ quoting an unnamed NATO official that Russia has lost 40,000 out of their 190,000 deployed troops (killed, wounded, prisoners). ISW then writes that those 190,000 are the majority of the deployable battalion tactical groups available to Russia.
There are some reports of the Russian National Guard internal security forces being deployed, but I can make no sense of the numbers. Are the deployed numbers of the National Guard significant (presumably not included in the 190,000 estimate above) and have they suffered significant losses (on top of the 40,000 estimate above)?