[ZXT10D]

...looked at the little window for oil and it looked completely empty....

What kind of bike is it? Did you check the oil with the bike on the sidestand?

I put in another 4 quarts today without draining the rest and I might’ve screwed up big time.

That would be a radical overfill, possibly enough to damage the engine or
emission control systems on newer bikes.

what could I have done....?

Stop using the bike until you find out how much oil is in it.
Check the owners handbook or service manual for details.
For bikes with a centre stand and a sight glass, checking the
oil level is very easy. If you only have a side stand, it can be
very difficult to check unless you have an assistant to hold
the bike vertical while you check the sight glass or dipstick.

Hopefully it will be ok when you remove the excess oil. Good Luck.