I just had this done to some shirts. The cuffs were too large, and too loose. It is more of a job than it first appears.
I first thought that the tailor could simply sew up a bit of the bottom of the hole on each side, and extend it at the top to compensate. That was going to look pretty bad, and would not solve the large cuff problem.
Hold the cuff as if it were linked closed. Then move one side up so that the bottom fabric edge makes contact with the top of the hole from the other side. I believe that is the amount that will have to be removed - at a minimum. Then a new hole will have to be cut and bound. It will also require removing the cuff, adjusting the placquet, and maybe the sleeve diameter.
Button cuffs are easier to adjust a bit.
An alternative I did not look at - and should have - would be to simply convert them to button cuffs while they are removed.