event pass question

mission:Deal 5000000 damage while being Mutant
5000000 damage?  the hero hp 10000, so 5000000/10000=500, if 17 round I kill 10 heros 500/10=50, 1 gmae need 2*17=34min 34*50=1700min 1700/60=28hour ?
this is only under the most ideal circumstances, so I need to spend 40 hours to complete....