Pattern question

i have got to a part on my pattern i dont understand can u help me pls?
it says
worlking st -st throughought inc 1st at each end of 5th row and every foll 10th row till 39 st.
is that at 5 10 15 20 25 ect or just 5 10 20 30?

No, you will increase one stitch at each end of row 5, and then every 10th row after that. So on row 5, 15, 25, 35, 45, etc. until you reach the correct stitch count.

oh doh thanks!