Problem lPmmH

After S21, site tells me "Continue...", I make the move S22 and site says "That is not that move" and I lose scores (-11). But if king hits spear, horse can hit 32 and that would be mate. Site offers mate throughout 2 moves, it's not shorter, than my mate. I've found the best move and the extension, leading to mate. My mate must be taken by the site. There's the mistake in this problem.

the gold can capture the silver dropped on 22. you can turn on the engine to check for other solutions

I guess puzzles do also take care of piece value on your side

@Olekaze you're right, I was wrong.

@Rainfall thanks for your opinion!