Amumu's E vs. Tristana's W

Playing Amumu

enemy Tristana low on health

she is at max range for banage toss, I still hit her

after I connect, she jumps away.

(not sure if intended) I moved (aprox.) an inch towards her prior to jump, (aprox.) 4 inches away when she activates jump, after jump I stopped (aprox.) 4 inches away from her

(even if the above is intended to work that way) I was spamming tantrum during the bandage toss it still hit her even though she was clearly out of range.