You're running 20/4 and that's perfectly fine for veg! You can keep it like this with no problem. If you want, you could switch to 18/6 later to save a little energy and give the plants a bit more rest, but it's not required.
There’s also something called DLI (Daily Light Integral) – you can roughly use it as a guide, but honestly, the best way is just to watch your plants. They'll show you better than any number when they’re happy!