What does 11 ct mean?
11 ct means a coarsely woven fabric.
Ct (from 8 ct to 35 ct u sw) indicates how coarsely the fabric (canvas) is woven. The larger the numbers, the finer the fabric.

The holes on Aida cloth are not as large as on canvas or straggler. Thin cotton threads are typically used for embroidery on Aida cloth.
All fabrics are divided into three categories: Coarse, Medium and Fine (a table).
Rough: up to 12.5 ct
Average: 13 ct - 16 ct
Fine: from 18 ct
Embroidery kits for large stitches (9 ct, 10 ct, 11 ct, 12 ct)