The battery state of charge reported by a BMS or battery monitor is only an estimate. At 199.81 amp hours on a 200 amp hour battery, it is clearly within 1% of full, but the cells may still be accepting some more charge. And it is very possible that amp hour count has drifted off as well. My JK-BMS has drifted the other direction. When my cells are near full, the BMS is only reporting 40% state of charge now. Each BMS or battery monitor has it's own rules for what must happen to trigger a reset to full 100% charged. In most cases, it is a combination of the voltage reaching a full threshold while the charge current also falls below a certain level for a given amount of time. Once it does a reset to 100%, it literally counts the amp hours removed during discharge to estimate how much is left. In a perfect world, if you discharged 40 amp hours out of a 100 amp hour battery, it would be at 60% state of charge. But what if the battery capacity is really just 98 or 102 amps hours? Or, when it the current sensor is a little off calibration? And what about some resistance loss that is losing power while charging so if thinks more power went into the battery but some of it was lost as heat? Each cycles that does not trigger a 100% reset can cause the state of charge to drift away from perfect. That is what happened on my JK BMS. After about 20 cycles, the SoC drifted down about 20%. But I know from the cell voltages that it is hitting 90% each day from sunlight. But for some reason, that is not causing the BMS to reset the SoC counter. After several months, mine got to where it was hitting zero SoC each night, even though the cells are really just dropping to about 50%, again, confirmed by the resting cell voltage and the fact they are hitting the absorb voltage after the correct amount of charging. So now each day the MPPT charger goes into float, the BMS only shows about 40% SoC. That sort of makes sense as I am trying to run the cells from 50% to 90% on daily cycles. That is a 40% change, so when it drifted down and hits zero, the charge pushes it back up to 40%. I have tried a few things to get it to reset back to 100 when full, but still no luck. I trust my voltage readings, and the Schneider charging to absorb limit, and the MPPT charge controller going to float.