When those who want to get support for my product pay an extra fee, why can’t we get this fee?
The total price would be the same if it’s supported or not. If you enable/offer item support :
If you DON’T enable/offer items support :
We have provided this service to those who want to get extra support, our customer has paid, but why doesn’t CodeCanyon pay us this fee? Please see the picture I posted There is an outstanding charge of -3.76$ under the “Fees” category.
Whoever bought your item did not purchase extended support, so you didn’t get any more money for it. The initial 6 months of support are included in your $10 price tag.
It seems you sold two licenses at $6 each. The CSS category has a fixed buyer fee of $1 USD, so you effectively got $5 for each purchase.
Then, as a level 1 author, you’re subject to a 37.5% author fee according to the fee schedule. Thus, for each $5 sale, you’ll pay $1.875 in fees, which adds up to ~$3.76 (with rounding) as shown in your screenshot. It has nothing to do with support extensions.
On top of that, you had another $1.50 withheld for taxes. This leaves a grand total of $4.74 as you see in your screenshot. Everything is working correctly here.