Ukrainian losses in the east are well documented. From another article today in the Kyiv Independent:

Russia has captured 1,146 square kilometers (442 square miles) in Ukraine since Aug. 6, about a quarter more than in the first seven months of the year, the media outlet said. The Russian military also advanced by 200 square kilometers (77 square miles) over the past week, Bloomberg reported.

As Russia makes gains on the battlefield, Ukrainian officials are growing more despondent about the future course of the war, according to one official close to President Volodymyr Zelensky’s office who spoke to Bloomberg.

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31,000 Ukrainian KIA, with Russia’s estimated KIA ranging from 100k to 200k.

There aren’t official public Ukrainian stats on this. There are various estimates. The US estimates about 70K. An anonymous Ukrainian official told the WSJ it was 80K last month. I can’t tell where their 57K comes from, but it’s a bit lower than most estimates. It’s definitely not an outlandish number though.

I’m assuming your 31K is from a public statement from Zelensky in February. Here’s another Kyiv Independent article that examines that public statement about casualties – and the difficulty of getting accurate information. Even in March they said that estimate was “significantly lower than some recent estimates published by sources outside the government in the absence of official data.” And that was more than 8 months ago.

I read that more as “at least 500.”