First off let’s determine the difference between a trouser cuff and a trouser fold.
A trouser fold is when you solely fold the ankle of the pants the way you want it and it’s clearly possible to put them down again.
A trouser cuff, on the other hand, is a sown fold. The cuff has to be folded in the opposite way than normal to prevent the inner lining from the trousers to show (like the inner thread shows when you fold your jeans).
A trouser cuff can be created in more or less two ways:
The tailor can fold the trousers and attach them where the fold starts by the ankle, this creates a fake cuff. This is done to trousers which lacks length material.
A real cuff is made as mentioned above. It is made by folding the trousers the opposite way and again the right way. Inwards, outwards. Then it’s attached by the inner part of the lowest point on the trouser, before pressed to make it keep fresh and folded. Try looking in a store if it’s hard to understand how I am saying it. In fact it’s quite hard to explain.
When it comes to the hight of the cuff I have 5 cm as a favorite measurement.
If you are having problems with your tailor not understanding you properly I would suggest you to try it yourself and show it to him. Yet I have never met a tailor who doesn’t know what a trouser cuff is. It’s like me telling you I don’t know what Tumblr is.
I hope this helps!