I can guess they "use" each one for each currency accepted: #1 GBP; #2 EUR; #3 CHF; #4 USD
To comprove that i must do 3 buys, and i don't want to do...  
If that is true, then i cannot imagine they sold as many orders in EUR than in CHF...  one more nosense...

BTW, the more i see from yesminer the more i think this is a total SCAM. There is no doubt (or not reasonable doubt)... But if somewho can show any proof of the REAL existence of this miners, i'll send my apologies to yesminers...