You got a little extra from the grains, or the LME gave more than the recipe expected (LME is not as standardized as DME), or you boiled longer or harder than the recipe anticipated. Or a little of all of them. If you have 5 gal. at 1.060, then you could have added 3 qts-1 gal. of water to get it to 1.051. Not sure if you had that amount of room in your fermenter. Either way, it will be fine, 1.060 is not that far from 1.051, just a little more alcohol in the end.