Stumped Again

Please help the pattern calls for the following:

Ending with RS row. I take this to mean I complete pattern on the RS, so that the following would begin on the WS, right? (WS will have sts begin for one shoulder at arm hole edge and other shoulder begin at neck edge.)

Shaping shoulder: Cast off 10sts beg next and alt row. Work 1 row even. Cast of rem 10sts. With WS facing, join yarn to rem sts and work to correspond with other side, reversing all shapings.

Yes, that’s the correct side to begin on.
You would cast off 10sts at the armhole side on the WS row, continue across, turn and work back. Cast off 10sts again at the armhole side and work across, turn, work back for the one row even and then again cast off remaining 10sts.
For the other side, join a new end of yarn and work the WS, turn and cast off 10sts at the armhole edge (this time on the RS), work the row, turn, work one row back to the armhole edge, turn and cast off 10sts, and repeat working the rest of the row plus the next row and then cast off at the armhole edge again.