I have a bathroom counter top that is 60 cm. I plan to put a over the counter sink which is 30 cm deep. Normally the sink drainage pipe is installed at 60 cm. If my counter is at 60 cm in this case, what height do I put the drainage pipe at?

I'm not sure what an
over the counter sink is. I think I know but not sure.

If I'm converting 60 cm correctly that's 23 inches, almost on the floor.

Assemble the sink, the sink drain with the tail pipe and the trap. Measure from where the sink will sit on the counter top to the opening in the trap. That will tell you how far below the counter top the drain pipe has to be. Make you drain pipe out of the wall lower that what you measured. You can always get a longer tail pipe if you are to low. You can't make it work if your drain pipe out of the wall is to high.