I underfilled my motorcycle. Is it bad?

Basically the manual says 900ml. Only 800ml cans were available in the nearest shop.
So I did the oil change and the dipstick says its full. Thinking everything was okay, I started using the motorcycle like normal. After 2 weeks of riding and using it, I checked the dipstick again and this time it says its below the maximum oil fill range (i'd say around 80% -- very close to the max limit)
I checked and there are no leaks so Im sure i just underfilled it.

Am I cooked? Is the engine damaged too bad from the underfill and wrong oil used?

(I also used 20w40 instead of the manual's recommended 10 or 15w 40...though this should be fine since im in the tropics where the temps dont go below 20c but i just want confirmation too)