The TBPARM bit in the Configuration Register CR1 will tell you whether the 4K physical sectors at top or bottom.
The default value is 0 which is bottom. The desired state of TBPARM must be selected during the initial configuration of the device during system manufacture; before the first program or erase operation on the main flash array. TBPARM must not be programmed after programming or erasing is done in the main flash array.
So if you did not configure initially then the default value is zero and you should refer table 7.1 otherwise table 7.2
since you are using 128S if TBPARM is "0" it will be Table 7.4 for bottom and 7.5 if TBPARM is "1" .
Please refer page 52 in the datasheet.