If it's running more than a minute or two a day fast, likely it needs more than a regulator adjustment.
Typically a watch will run fast as the oil goes gummy or the watch gets dirty since there is less power transferred through the train. This causes the balance rotation to get less and less, hence taking less time between "ticks".
Always a clue to clean a newly acquired watch when the regulator is pushed all the way slow....
The regulator essentially lengthens or shortens the hairspring as it moves between the hairspring stud and its maximum adjustment. A shorter hairspring moves faster a longer moves slower. The range varies greatly as some watches have very long hairsprings.