Can you explain what is "0.075% notional"? Is this calculated based on entry price or based on close price? Or both?

And how it is consistent with the "-72.000000" I see here:

The current BTC price is 7620. So 0.075% would be 5.715. And this number -72 is totally different.
Also, when I pay the fee ($3.50 per lot for forex, 0.075% for BTC, etc) - when I open the position, when I close it, or both?
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When the customer buys indices do you pay dividends of the underlying stocks in the index (and deduct dividends when the position is short)?