they've probably listed it at what the estate agent has recommended based on the market. They don't need to have done 225k of improvements for it to be worth 225k more now. I mean, whether or not it is actually worth 225k more now is debatable but a lot of the time people negotiate lower so they may be putting it up higher than they think they'll get in the end.
I did nothing to my house so it was actually in a worse state than when I bought it, but a few months ago I sold it for 200k when I bought it in 2018 for 130k. I'm in Manchester. The house we bought was 375k and the owners had bought it for £190k in 2012 so it had basically doubled in value in 10 years - absolutely nuts but that was pretty much standard for everywhere we viewed, and we were looking in multiple areas of Manchester.
not saying any of this is right btw, the situation is actually horrendous with how much property has gone up and it's not proportionate to wages. I'm extremely lucky in that I managed to buy my house at the right time and values shot up, because if I was buying for the first time now I would have literally zero chance of being able to afford anywhere here whatsoever