The hotel you can stay at for kami con says Rates:

Single: $119

Double: $129

But what exactly does this mean? i have an idea but not sure.

It refers either to the bed, either single or double... or the occupants.

Most likely it means 1 person or 2 persons. Most American hotels charge the same rate for 1 or 2 people. And again, most American hotels have either double, queen, or king sized beds. They sometimes charge more for the king. If kami con is not in the US I would go with the number of people involved.

Single occupancy (one bed) or Double occupancy (two beds).

it means $10 more for another person in the room

The hotel you can stay at for kami con says Rates:

Single: $119

Double: $129

But what exactly does this mean? i have an idea but not sure.