WinMiner base currency is USD. That means that your balance (in USD) is guaranteed and protected from coins fluctuations. To do so, WinMiner exchanges coins mined into USD.

When a user wants to withdraw, we take the balance (in USD) and carry out the user withdrawal order, whether a PayPal transfer (in USD) or BTC or ETH (in which case we purchase the coins for the user and make the transfer).

When buying ETH or BTC using USD a fee is imposed by the exchange, usually in the form of an exchange rate. In your case the exchange rate was ~400USD for ETH by the exchange.

Deducing our fees (3% = 1.5USD) and the ETH transfer fees (~0.2USD - you can verify that looking at the block explorer for your ETH transfer) from 50USD brings your net to ~48.3USD.

~48.30USD would buy you 0.12069685 ETH at the exchange and this is the amount we transferred to you.

Hope this clarifies.

BTW, at the request of our users we are working on adding a feature that will allow users to choose their own base currency - that way a user that wants to be exposed to the volatility of a certain coin and would want to withdraw in that coin could keep his balance in that coin and avoid exchange costs.