Hi Oscar,
THats Correct. When you have the reset method setup, the accrual is calculated based on Cumulative basis. If you want the difference procedure, you can do so by changing the Accrual/Defferal method.
In your case, now overtime you run TPM44, it will be calculated from 17th Apr till the key date. For TPM44 on 30th Apr, its always based on the Position Value date.
In case your Position Value date for the Purchase was also 4th May , then TPM44 would not have given any output.
Regards,
Nikhil