First, the smart contract was faulty from start, and AMPL and AAVE are responsible for this.
In order to make an absolutely correct calculation, it is necessary to perform a huge and unrealistic number of calculations, taking into account absolutely all input-output transactions, based on an erroneous contract. Also, at what speed in each second the % increase was received for investors. Take into account the rebasing every day, and how the error in the smart contract affected this during negative-positive rebasings. All these calculations can only be made approximately and not absolutely accurately; now it will simply not be possible.
Therefore, the calculations that are offered to us are approximate by default, and do not take into account all the input data that is necessary for an accurate calculation. Please also note, not understanding how the AMPL protocol works, that AAVE unilaterally has significantly reduced the already low % that AMPL depositors receive here -
and later once again here - [ARFC] AMPL Interest Rate Updates on V2 Ethereum