Carried interest payment is calculated across an LP's subscription period. The subscription period is the number of quarters to which an LP subscribes in advance. Depending on the options provided by the fund manager, an LP may have a quarter-by-quarter subscription period or a multi-quarter subscription period.
If on a quarter-by-quarter subscription period, the LP must be repaid only the amount they contributed to the quarterly fund experiencing the exit before that LP begins to pay carried interest.
If on a multi-quarter subscription period, the LP must be repaid the total amount they contributed to all quarterly funds within that subscription period before that LP begins to pay carried interest.
For example, an LP has a quarter-by-quarter subscription period and has contributed $10k to three separate quarterly funds, for a total of $30k contributed to the Rolling Fund program. If the first quarterly fund has an exit, the LP will begin paying carried interest only after receiving in distribution their initial investment of $10k they contributed to that particular quarterly fund.
In contrast, if that LP had a three-quarter subscription period, they would need to receive in distribution the full $30k that they had contributed over that subscription period before paying any carried interest.