I have this textbox here. And I just do not understand the magic, why "PM" is smaller? Though it seems just normal text on the left side.
I'm not a Sketch User
Typically in most apps layers don't resize their names in the panel/list.. I mean the layer name doesn't become 30pts tall simply because the text is set to 30pts. That's not how User Interfaces work.
Chances are the text is set at a different size. Select it with the text editing tool and then check it's size.