Pools and payouts
One pool per market
BTC and SOL each have their own pool. Losses go into the market's pool, and winning trades are paid from it. One market's results never touch the other's pool.
When the pool is short
Your collateral always comes back at once. If the pool can't pay all of a profit right away, the rest waits in line and is paid as losses come in. The line is first come, first paid: whoever closed first is paid first, a partial payment keeps your place, and nobody behind you is paid before you. Your place and what is ahead of you are on the portfolio page.