This depends on your account type.
EOD Challenge
Evaluation: none.
Funded: 2.5% of your starting balance, so $1,250 on a 50K, $2,500 on a 100K, $3,750 on a 150K.
Sprint Challenge
A daily loss limit applies in both phases, at the same percentage in each.
25K: 2.4%, which is $600
50K: 2%, which is $1,000
100K: 2%, which is $2,000
Instant Classic
3% of your starting balance, so $750 on a 25K, $1,500 on a 50K, $2,250 on a 75K, $3,000 on a 100K, $4,500 on a 150K.
Flex Challenge
None, in either phase.
What happens when you reach it.
The daily loss limit is a soft breach, not a hard one. Your open positions are closed and the account is paused for the rest of the trading day. It resumes automatically on the next trading day, and the account is not closed.
For the exact figure on your account, check your dashboard.