How to deal with strange width calculation in fieldset?

Question

HTML

good afternoon, dear site building gurus,
I'm trying to fit a form into a pop-up window, where there is a fieldset tag. at the same time, browsers somehow strangely calculate the width of the form with this fieldset and as a result a scrollbar appears. the object inspector shows that the width parameter is not set anywhere, but this width turns out to be much larger than necessary. Please tell me if there are ways to deal with such country calculations in browsers

Answer 1

Instead of padding, do you have a block stretched?