The i7 7700 is a low wattage CPU, draws maybe 65W or so MAX. (This is not the i7 7700K that can pull 100w...)
The GTX 1050 is a low wattage GPU drawing around 70W.
So we are only talking about 135W, add some for the MB and etc and maybe total system draw will be around 200w MAX and that's over estimating.
So that 300W PSU is fine for the current setup being an OEM machine. It's basically a simple workstation box for the most part, even with the GTX 1050 in there.
Now throw a GTX 1060 6GB in there and he would need a new PSU.
And the machine in under Warranty since it's NEW so he is covered.