Sellers can choose up to 5 (Five) different cryptocurrencies. BTC, however, will be one common currency for all the products, which means among the five different currencies from which buyers can choose BTC will be available by default. This is because all the products may not support payment of the same currency.
For instance, a buyer added two items to purchase, items A and B, and both the items are of different sellers.
For Item A, seller added payment currencies as BTC, XEM, XPR, ETH, LTC
For item B, the seller added: BTC, PAX, USDT, DASH, GMC
As we can see if the buyer wants to pay for the both the items at once he/she will have to use BTC as it is the only common currency accepted by both the sellers.