When it mentions that you can spend 1 sorcery point to double its duration, up to a maximum of 24 hours, does it mean that every time you spend a sorcery point you add the original duration again? Or does it exponentially double the duration?
For example, if I spend 4 sorcery points on a 1 minute spell, does it become 5 minutes (1 minute duration added four times) or 16 minutes long (1 minute doubled four times)?
What I meant by this question is just using Extended Spell on a spell once, but using more than 1 sorcery point on it as per the metamagic's description.
I know you can't re-extend a spell if it's already active, but I'm talking about the initial casting, where you can spend multiple sorcery points to double the spell's duration.