The notation "Interest Buy/Sell: -7% / -7%" in your leverage account indicates the yearly interest rate applied to your positions. A negative percentage signifies that you will incur a cost for holding a leveraged position overnight.
How to calculate interest?
<Opening price> * <Position volume> * <Interest (%) / 100 / 360>
Example:
Twitter: 100 shares, long position, interest - 7%
25 * 100 * (-7%) / 100 / 360 = (-0,49) USD