Would the nuance of this sentence change if I replace "what" with "about" here?

Native speaker’s answer
Rebecca
Yes, the meaning would change slightly if you replaced "what" with "about" here. "What" does not by itself express an estimate or an approximation like the word "about", but it is instead used here to get confirmation or verification from others. It is kind of like asking a hypothetical question which does not require a response in a very informal way. Ex: It was what, twenty years ago that she died? Ex: We have only what, two weeks before we move and a lot to pack.