5 inch berenguer knit hat

Usually I just knit away and let the pattern go where it may and hope I have a doll that can wear it.
However, if I just want to have it come out even in shell pattern, 7 stitches + 2
cast on 30 - is there a magic number to increase cast-on to?
I tried to go by 9’s - didn’t work.
I afraid I will have to rewrite whole pattern to figure it out.

It seems that the pattern multiple is 7 + 2. For 30 sts that would be 4x7=28+2=30.
You could do 5x7=35+2=37 or any other multiple x7 then +2.