A Bank of Japan training document calls the change in present value when the rates for all maturities rise by 1bp BPV (basis point value) and computes it as the present value after raising the rates for all maturities by 1bp minus the current present value. That document describes BPV as the "decrease in present value" (our translation), while its worked example shows BPV as a negative number. When comparing figures, check the direction of the sign and which rates were moved (the fixed rates of market swaps or spot rates).