if you hold 5 bitcoin in your wallet on the snapshot time(august 1st), then you have 5 bitcoin and 5 bitcoin cash. they are totally independent so you can sell/send 5 bitcoin cash and still keep the 5 bitcoin. you should not add up the values because they have different values. currently 1 bch=0.17698500 BTC
Is that true, that you can exchange both 5 bitcoin and 5 bitcoin cash for the fiat? That means pretty much money, as 5bch = 5*0.1769 = 0.8845. 1 bch is $1300 so you end up with around 1000 dollars in fiat and still 5 btc?