GTX 780 + 63 overvoltge?

Okay so here is the deal. I have two 780's in SLI and am doing some overclocking using Precision X. When I went into the voltage settings I noticed one card could overvolt +38 (Which is normal from what ive read) and the other +63. So I am wondering Is there something wrong with the one that can overvolt higher or am I lucky and will get more head room for overclocking or is it even safe to overvolt that high should I stick to +38? I am pretty new to overclocking and just getting my feet wet so any help would be appreciated. 

Update: After talking to EVGA turns out I have a non super clocked part with a super clocked part number. I am talking to EVGA to see what they will do to get the part replaced with the correct part but its not looking good.