Chart Knitting Question

I’ve knitted for years, mostly written directions except for picture or fair isle knitting.; I recently bought a book on knitted lace shawls and the charts are puzzling to me. I searched through the book and it doesn’t explain further, so I might be the only dense person who needs clarification. My question it this: part of the chart is explained at the bottom as “rep” [section of chart shown] “work rep only when working in round” Sometimes this is a very large section, other times, a small part of the chart.

Your help would be very much appreciated. Thanks.

Rep stands for repeat. If there is an increasing number of sts or if there is a section of the pattern that repeats, not all the repeats will be charted. It sometimes helps to look at the number of sts and then to work out the number of repeats needed to use up all those sts.
What book are you looking at?