When i play while recording the game, it runs at a smooth 60fps. But when I play the recording back it seems to be in slow-motion. What's happening?

Specs -
Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
NVIDIA GeForce GTX 1060 GDDR5 @ 3.0 GB (192-bit)
930GB HD
12GB RAM