Strange min raise issue

[Thunder]

Blinds were 30/60, UTG raised to 120 and as I went to reraise, I noticed that the min was 240 or something like that. As the min bet at this level is 60, why wasn't 180 available?

[Muzzard]

The min re-raise size is equal to 2xthe previous raise.

EXAMPLE A
So UTG raised 60, so you have to raise 120 on top which is equal to 240.

EXAMPLE B
If UTG raised to 180 total, that is a raise of 120 from the BB, so you would have to re-raise 240 on top which = 300

This could be room dependant, I'm not sure. Some people insist that you have to double the previous bet, not double the previous raise size. So in example B the raise would have to be 360 total, min. Example A would remain the same 240 total. But, I'm pretty sure the first option is the 'standard' option.