I was at a transmission repair shop for a new rear seal, and I checked the fluid before I left and there was too much fluid in it. The vehicle was cold and when I checked the stick it read enough and more if the engine would have been hot. The person from the shop checked also and confirmed he told me doesn't matter but if I wanted he would spoon some off. Why does it not matter on a transmission but with engine oil you should not over fill? Why have the stick with readings and then if your not in the readings it would still be all right? I don't understand why you would have the readings if it didn't matter? They have holes punched in the stick so you can tell correctly your fluid level.

Too much fluid will cause fluid to foam and vent out the top vent cap on your trans.
But this would have to be a significant amount of overfill.
Slightly over on the stick mark isn't cause for alarm and I'm sure your trans guy will take care of that.
But yes, those marks are there for a reason.
Engine oil level is critical. Too much or too little can cause serious damage.
I'm sure others will be along to add their comments.

It does matter. Overfilling can cause foaming, where the fluid has air in it. It will then not lubricate and carry away heat from the bearings properly. Overfilling can contribute to overheating, the enemy of automatic transmissions. Internal pressures can also get too high, where the fluid will force its way through bearing seals. Overfilling is always dangerous.

It absolutely does matter. That is why you have marks.
It's irresponsible and just plain downright sorry that someone from the shop checked it and said it didn't matter.

For future reference, I'd start now looking for another shop to do my repairs. Be sure you ask for their credentials and ask about their warranty policies. It's your hard earned money paying their wages so they should have no problem discussing these things with you.

I double checked it and had my regular mechanic check and went back to the transmission place and had them take out the overfill. Thanks!