Filing tax as an artist in gallery

I'm a concept artist working for studios for years. But recently I started having some of my personal work exhibited for the local gallery. A few weeks ago I received the form 1099-NEC for how much I earned and it really confused me.

In 2020, some of my work got sold for an A amount of money. The gallery charges 30% plus an extra fee every month ( let's call it B.) What I received is the C amount of money.  In a formula, it looks like this: 

(A x 0.7) - B = C

But it surprising to me is, what was wrote down in the 1099-NEC form is the A amount of money. I expected an amount of either C or B+C ( I understand that B is still my earning). It ver confused me. Is the gallery's sale commission counted as their income? What I received for my income is the B+C amount but now based on the 1099-NEC, I have to report the tax as A? Is the gallery being deceiving to artists for tax evasion since now the artists have to pay that amount of income tax for them?

If anyone can help to explain this to me please, it will be appreciated.

Best