How do you know the nds games's card size ? Well, all you can do is multiply by 8. Look:
4kb EEPROM ==> Set it to EEPROM 0.5kbytes
64mbits EEPROM ==> Set it to EEPROM 8kbytes
512mbits EEPROM ==> Set it to EEPROM 64kbytes
2Mbit FLASH ==> Set it to FLASH 256kbytes
4mbits FLASH ==> Set it to FLASH 512kbytes
256mbits FRAM ==> Set it to FRAM 32kbytes
ENJOY!
4kb EEPROM ==> Set it to EEPROM 0.5kbytes
64mbits EEPROM ==> Set it to EEPROM 8kbytes
512mbits EEPROM ==> Set it to EEPROM 64kbytes
2Mbit FLASH ==> Set it to FLASH 256kbytes
4mbits FLASH ==> Set it to FLASH 512kbytes
256mbits FRAM ==> Set it to FRAM 32kbytes
ENJOY!