Open the export using a hexadecimal viewer / editor or use the viewer of the programmer to see the data
Empty / unused area will usually be full of either 0xFF or 0x00 bytes.
So for example, if you see random bytes in the first 128 KB range and then everything is FF bytes, there's a good chance the circuit or whatever used that eeprom reads and writes data only from the first 16 KB
See picture below, where I use HxD (freeware hex editor / viewer) to open a random binary file ... it shows 16 bytes per line, and on the far left column it shows the offset in the file - the last fully visible line in the picture has offset 0x 0000 0200 or 200 in hexadecimal, which is 512 in decimal ... so if I see only FF or 00 from that point, I could assume only the first 512 bytes are used by the device or that it was actually a 512 byte eeprom chip and not a 64 Kbit (8 KB) chip.