Questions about ds1/l/q on p_data_t0

[chirst3]

The product I'm currently using is LakeSP Version D. I'm facing a significant issue with the algorithm. After reviewing the LakeSP PDD and ATPD documentation regarding SWOT water storage data, I encountered a point that I find perplexing.
Their water storage data is presented as changes in water storage: ds1/l ds1/q. However, the official documentation states that changes in water storage are relative to the water storage at time t0 , specifically p_date_t0. Calculating it as using ΔV - p_ds_t0 yields the storage change. Yet, p_ds_t0 is officially defined as the storage change calculated relative to changes in the reference water level and area , and then treated as the storage change relative to the day p_date_t0.
So the question arises: if p_date_t0 is 2023-12-3, shouldn't ds1 for that day be 0? the row I selected corresponds to December 3, 2023. On that day, ds1 is not 0. I just can't figure it out. If you're using p_date_t0 as the reference, then the △V should equal the p_ds_t0 value for that day. Yet, after reviewing numerous files, I found that ds1 values for p_date_t0 are never zero.
So where exactly is the problem?