What kinda INcrease are we talking about?

knitting a hat but i want to make a rounded brim

http://i-like-lemons.blogspot.com/2008/01/button-tab-hat-pattern.html

The brim tab can have a rounded edge by doing a one stitch increase at the beginning of rows 2, 4 and 6 and then doing a corresponding one stitch decrease on rows 8, 10 and 12.

Probably a M1 increase in the bar after the first stitch would work best.

For the decreases, a ssk decrease will lean left and a k2tog will lean right, so depending on which edge you’re on for the start of the row, do the decrease that will work best.