Rebuilt alternator puts out 12v at idle

[Jon ah haha]

I recently got my alternator rebuilt for 185 amps at a local alternator shop and at idle it puts out 12v and drops under 12 with load. <1000 rpm 12v. 1250 rpm 12.7v. 1500 rpm 13.8v. 
When I got it back from him it wasn’t putting out right so he put on a smaller pulley and he says this is what it should be at. Is that right because that doesn’t seem right to me but idk
It was originally an 80 amp and is on a 96 Tacoma 3.4L