The High-Water Mark (HWM) for each follower is different. For example, a follower A who joins the offer on May 5th may have a different HWM compared to follower B, who joins on May 6th. If the provider has trades on May 5th, follower B has not yet copied those positions, so the HWM for follower B will not include the trades from May 5th.
Additionally, the HWM includes "floating PnL," meaning that when the current interval is settled, the floating profit or loss will also be factored into the HWM. This explains why the provider might have concerns when nearly all trades are eventually closed with profits, yet they still receive no PMF from some followers. When the interval ends for certain followers, the "floating loss" may be significant, and it will be included in their HWM calculation.