Armhole decreases

Hi there - I have successfully begun to decrease by casting off the first 6 sts in consecutive rows etc. However, the pattern then said to decrease 1 st at the end of the next 3 rows, which I have also done. Then it says to dec 1 on foll 2 alternate rows then on following 4th row. I am confused on two details:

1 - if I decrease on every alternate row then i am always decreasing on the same armhole - won’t this harm the symetry?

2 - the pattern says i should have 87 sts after the first 2 decrease rows (I do). It then says I should have 75 left after the final decrease. However, the above instructions look like they only decrease the sts to 81. Does this mean I should carry on decreasing every 4 rows until I do reach 75? If so I would be decreasing on the same side every time.

Help!!

You were most likely supposed to decrease at each end of the rows so you would have decreased at the beginning and end of the designated rows.

That would give you the correct stitch count, too.

The bind offs are only done at the beginning of the two rows because you can’t bind off at the end of a row. After that, armhole decreases are done symmetrically on each side.