Different Tempos in Logic Pro and VCV

This might’ve been mentioned before but I couldn’t find it. 
I am no expert but I have a question that has been bugging me for a while. 
I have synced Logic Pro and VCV using the IAC driver so I can send MIDI to VCV 
from Logic. After some faffing about I got the two to start and 
stop using Logic transport. My question is the tempo.
 Even though the two are in sync the tempo in VCV is about 
10 BPM more than in Logic. I can’t work out why. 
I am sure it is something fairly simple but I don’t know
 enough to fathom it. 

Thanks in advance.

Just a shot in the dark but could it be the sample rate?


Thanks that’s sorted it. I should have checked that first!!

Thanks again.