Thank you for contacting Cypress Community.
Table 4 of the datasheet shows the address for each sector that should be provided during sector erase command. Whichever bits are mentioned as 0 or 1 should be followed. The rest of the address bits which are mentioned as X are don't care. Means the least significant bits get neglected. For SA3, a range of address has been shown. So, if we provide any address within the given range then it should erase SA3. Table 10 of the datasheet provides the command sequence for Sector Erase command and Figure 2 gives the flowchart.
Could you please elaborate a little on your question? Are you operating the device in word mode or byte mode? I would like to inform you that if byte mode is selected, then the DQ15 line acts as the least significant address bit (A1). How are you verifying whether erase operation is completed successfully or not? Are you able to read data from other sectors?