Also, setting both values to 0 will make unit still play it's animations, but those can break if there are other orders (Such in a situation where there are nearby enemies, making hero break the spell animation to attack, which again, displays attack animations).
If you set both to the same value, then the animation can't be interrupted or broken by ordering a unit to move or stop, like with the engine of Fan of Knives.
If one is higher than the other one, than unit will still play it's animation until the higher set value, but it can be broken starting from the moment of lower set timer.
I hope this helps you to understand these better.