You enter the amount of ETH you want and it will determine how much it would cost. Alternatively it is possible to enter the level of fiat you want to spend. The platform will estimate how much ETH you will get. Learn much more about the denomination of Ethereum https://financefeeds.com/bitcoin-holders-flock-to-new-presale-as-analyst-calls-btc-bull-token-the-best-copyright-to-buy/