Can anyone walk through basics of 50% royalty deal

Can anyone walk through basics of 50% royalty deal.? If partner buys drug from CytoDyn for COGS plus 10 percent. Partner sells drug for agreed upon price leading to gross sales. Allowances are negotiated to define net sales. Partner pays 50 percent of net sales to CytoDyn? Or 50% of (net sales less less what they paid for the inventory)?

Say net sales is 100. COGS is 20. COGS plus 10% is 22. Does partner pay CytoDyn 50 or 39 (100-22)/2 ?

Do I have this jacked up?

Then CytoDyn has to make small percentage payments to Progenics and Abbvie. Call that 10%, cannot remember the exact number. Does CytoDyn pass on 10 percent of what they receive from partner (10% of 50 or 39).? Or does CytoDyn pass on 10 percent of the net sales by parter? 10% of 100= 10.

I bet some of you business - lawyer types can set me straight.

Thanks