I would not worry about it, I would think for sure, and myself if I purchased that oil it's 5w-20, and they either made a mistake in the labeling, or maybe it's even part of a process they go through when changing jugs over... it could even be as simple as the jugs were molded for 10w30 which may be the biggest selling viscosity, and they used the jug for 5w-20... whatever the case I think you have 5w-20
If you happen to have 10w30 I bet also many many cars get filled with 10w30 at quick fills, yet I understand your standpoint as your taking the time, trouble, and expense to do this yourself correctly... but 10w30 still will not be the end of the line worse case scenario