Ascender, Descender and X-height box

When I’m creating a font there’s a guide box behind each letter.

It shows an ascender, descender and x-height line. I want to adjust this.

I can’t find anyway to do it?

Can someone tell me what I’m missing? : )

File > Font Info (Cmd-i) > Masters

Glyphs Mini:
File > Font Info (Cmd-i)

After you adjust the values, do you need to regenerate anything, or does it change everything automatically? I ask because nothing seems to happen when I change these values.

See screenshot here

Previous Ascender value was 750 and Descender was -250.

Context for this question:
We are using an open source font for an iOS app, but when you use it in text inputs it sits above the cursor. Apparently it’s an issue with ascender/descenders; so I’m trying to adjust them to see if it has an effect.

Thank you!

Not sure I understand the question. Custom Parameters override the automatic calculation, is that what you mean?

I was trying to adjust the vertical alignment as was accomplished here:

But no worries anymore, the developer just used the above method to fix it.

Thank you for your time!