What to put in column "postdest"

Hello FreePBX community! I’m new to freePBX, please go easy on me.

I just installed the FreePBX Distro, defaults, and I’m going for a bulk addition of extensions. My question is, what do I put on the column “postdest” of the csv file?

I have no additional dialplans or IVR destinations at the moment; pure, default unaltered new installation. I disabled voicemail for the moment, my clients don’t like it… I don’t know if that helps.

Thanks for reading, please, help! :S