There is an errata for this pattern.
BACK shape armholes should read:

Cast off 5 stitches at the beginning of of the next 2 rows. 71(76:86:91:96) stitches

Decrease one stitch at each end of next and 3 following 4th rows. 63(68:78:83:88) stitches

Then the amount left at the centre on a holder will be 29(30:36:37:38) stitches

The amounts for the FRONT are correct, until you get to the cast off of centre stitches after the heading shape right side
This should read: Cast off centre 5(4:8:7:6) stitches
If you need any help please don’t hesitate to contact me, Jane Ellison