What do they mean on Yoke decrease

Decrease as given on next and foll 4th rows 3 times in total and on foll alt rows 3 times in total, working straight in pattern on rows in between?

Hi and welcome!
Call the next row, row 1. Then you would dec on rows 1, 5,9,13 and rows 15,17, and 19.
The rows that aren’t dec rows are worked straight or without decreases.

Thank you!!