.sof to .pof conversion

Hi,

In quartus II I created a configuration file with extension .sof of size 1MB.

When I changed the extension to .pof file by selecting configuration device as CFI_128Mb and mode as FPPx8. the configuration file size increased to 16MB. Can any one tell me how the size of configuration files size increase like this?

If I use the configuration device as CFI_16Mb then the .pof output is 4MB.

How this changes happened?

I tried to create again by reducing start address and end address of the location. But still the 16Mb is there for the pof file.

Please help.

Thanks in advance,

Binu