Spoiler:
I had to do this dare from my master and if I fail I will be denied for 48 hours. I did not know how many 500 strokes were, but I thought I could manage this.....
So I tried it last night , but I did not cum. cumming from 500 strokes with only two fingers is really hard.
So I'm going to try again tomorrow, and hope I am horny enough then.