This is a very confusing instruction. I think it means to decrease 7 sts evenly starting from the first stitch and ending at the eight sts before last.
For example, if you have 100 sts on a row that you just knitted ( the last row), you then have to do decreases only on the first 92 sts leaving the last 8 sts undisturbed. So, you will have to do some math and see where the decreases will go. So you divide 92 with 7 and get 13 and 1 extra. So you will do decrease every 13 sts by knit every 12th and 13th sts together. Then you just work even on the last 8.