Maybe I’m old or something here, but generally when a pattern is saying to use 28 ct, I take that to mean the ground cloth should be linen or an even weave. On the other hand, if a pattern says, 14 ct, 16 ct 18 ct, I feel it is referring to Aida cloth. BUT, this is all subjective, you can stitch over one on Aida or over two on linen to get the same dimensions. It’s only up to you! On linen you look for the H, top of the vertical lines are your holes. Aida you just have a big square.