Hi,
I think your question is ‘what the difference is between 14 or 18 count fabric and 28-count fabric, yes? :)
If you have been stitching over ONE Square on 14-count Aida fabric, you would stitch over TWO squares on 28-count fabric and the completed picture on both 14-count or 28-count fabrics would be almost exactly the same size. Example: 28 count fabric divided by 2= 14 count
The same thing with 18-count fabric: if you stitch over ONE square on 18- count fabric, you would stitch over TWO squares on 36-count fabric.
There is a tutorial on ‘scarletquince.com” website that shows you a pictorial of the difference between ‘over one’ and ‘over two’ OR check on You-Tube to see if they have a tutorial.
Suggestion: practice going ‘over 2’ on a piece of 28-count evenweave fabric (Jobelan or Lugana)fabric till you get comfortable with it before doing any large projects.
Hope this helps. I am NOT an ECS employee but a stitcher that saw your question. :)