Sweater increase question beginner

"Shape sides
K10, knit into front and back of next st, knit to last 11 sts, knit into front and back of next st, k10.

Work 36 rows Inc 4 sts as before in every foll 12th row."

Question;

The stitches should increase from 104 to 120.
However, I’m confused as to the Inc 4 sts part.

Knitting into front and back increases by 1 stitch or 2?

If overall I need 16 extra by the end of the 36th row, how does it add up ?
It says ‘work 36 rows Inc 4 as before in every 12th row’, but on the first row I only increased 2, not 4.

Am I wrong or misreading it.

It’s a sweater Nico 665

Welcome to KH!
I wonder if there is a place earlier in the pattern where 4 sts are increased in a row? I agree that 2sts increased over 4 increase rows isn’t going to work.
What is the name of your pattern?

Rico design sweater 665

Seems consistently wrong over all 3 sizes. I would increase more frequently, 2sts each increase row as given in the pattern. If you alternate the 4th, then the 6th row (inc on rows 1,5,11,15,21,25,31,35) that’ll give you 16sts increased in almost 36 rows.