On each of the even numbered rows, for each repeat of the pattern after the asterisk, you are doing two decreases which aren’t made up for by doing any corresponding increases, so for each even row, you are going to have two fewer stitches per repeat. (When I say per repeat, I mean for each time you repeat the instructions after the asterisk.)
So, let’s look at each individual line.
Row 1: k5 *P11, K5, etc… <–Here the stitches in the repeat add up to 16 (P11 + K5=16 st.)
Row 2: P5 *K2tog, K7, SSK, P5, etc. <–On this row, you “lose” two of the stitches for each repeat, so instead of 16, you will end up with 14. (K2tog + K7 + SSK + P5 = 14 st)
Row 3: k5 *p9, k5, etc. <-- P9 + K5 = 14 stitches, which is what you end up with after doing the decreases on the previous row.
Row 4: P5 * K2tog, K5, SSK, P5, etc. <–The reason you only have a K5 here (instead of a K7 like you did on row 2) is because you lost the two stitches from the K2tog and the SSK you did on row 2. So you’d have 12 stitches in each pattern repeat. (K2tog + K5+ SSK + P5 = 12 st.)
So to continue on–
Row 5: K5 * P7, K5, etc. <-- P7+K5 = 12 st., which is what you’d have for each repeat after your decreases on row 4.
Row 6: P5 *K2tog, K3, SSK, P5, etc. <–You only have a K3 here (instead of a K5 like in row 4) because you lost two more stitches when you did the decreases on row 4. So for each repeat you’d have K2tog + K3 + SSK + P5 = 10 st.
Row 7: K5 *P5, K5, etc… <–Your repeat is for 10 stitches because that’s what you decreased to on row 6.
Row 8: P5 *K2tog, K1, SSK, P5, etc…
Row 9: K5 *P3, K5, etc…
So if you look at the numbers, you can see a pattern where the number of stitches K after the asterisk on the even rows, and the number of stitches purled after the asterisk on the odd rows keeps decreasing by two.
I hope this makes some sense. This is kind of hard to explain in writing!