ok we'll see if I'm a retard or not.
So apparently this strategy is called a short box which would simulate borrowing at a certain interest rate, but the interest rate is negative in my case so I would earn interest on taking this loan.
for explanation: the equity of this loan is worth the difference between strike prices 650-550 = $10 000, but I sold it for $10 500, so I net $500 for receiving a loan. wtf bro
see for yourself:
https://optionstrat.com/build/custom/SPY/.SPY250516C650,-.SPY250516C550,-.SPY250516P650,.SPY250516P550