If you have 0 pips available and no open trades, you have failed the level. If you have 0 pips available and one or more open trades, you cannot open a new trade until you either close an existing position or reduce the SL distance of an existing trade.

Example 1: I have 20 pips available. I open a EURUSD trade with a 10-pip SL. I now have 10 pips available. 10 pips are locked into the EURUSD trade, and I have 10 pips to risk on other trades.

The max SL I can place on the next trade is 10 pips. If I reduce my EURUSD trade SL from 10 pips to 5 pips, my available pips will increase from 10 to 15. But if I move my SL further away from 10 pips to 15 pips, my available pips will decrease from 10 to 5.

Example 2: I have 0 pips available and an open GBP/USD trade with a 20-pip SL. Because I have 0 pips available, I cannot open any new trades unless I make adjustments.

If I decide to reduce the SL on my GBP/USD trade from 20 pips to 10 pips, my available pips will increase from 0 to 10. This allows me to either open a new trade with a 10-pip SL or keep those 10 pips available for future trades.