Open Question: Hi I have found a job for the easter break but I have a few questions about the wages...Please help?

this is what the advertisement of the job says: Easter Fun Promotion, Dublin city centre, €350 per week basic & Commission....also one day promotions available I went to the interview today and the man said to me that whatever amount of money we collect, we get 30% off it... I don't understand. Im supposed to be working outside on the streets on saturday, from 10am-6pm, and say I collect like 10e in coins, am I only going to get like 3e for myself?? That would be unfair. Im a bit worried about that, to be honest. Should I still take the job or not???