1995 Volvo 850 overfilling trans fluid

Transmission problem
1995 Volvo 850 Front Wheel Drive Automatic 163K miles

Hello. I recently had my auto trans fluid changed and it was done by Mr. Lube. Unfortuantely the tech did not plug it back properly and it drained out and I could barely bring it back home. Luckily I did not go far. So they refilled it, but about a month later, I had my car checked underneath and found out the Auto trans. Fluid is leaking. I checked the dip stick for the auto trans. Fluid and found out they over filled it. What kind of damage can over filling do to my transmission and I will try to get Mr. Lube to take some out. Thank you for your help.