2019-08-01 · Shrimp sizes are denoted in numbers, such as 21/25 or U/15. When you see a “U” in the count, it means that there are “under” that number of shrimp in a pound. The slash between numbers denotes a range of shrimp in a pound. So, for example, U/15 shrimp contain fewer than 15 shrimp per pound. 21/25’s weigh in at 21 to 25 shrimp to a pound.