Not getting bonus IP

I have been playing many games celebrating 10 years of LOL with double IP getting several hundred IP a game. Before I start I'm not complaining I am just curious.

Suddenly after 4 games or so I went support Braum going 2 6 16 (maybe died too much) and got 120ish IP for winning. I'm wondering if either I literally got 60 IP as a support or the double IP didn't work correctly.

Does it make sense for a sup to get low IP like that or was I cheated out of double IP? How much IP do average supports get with a victory. Do assists give IP or do I need to pick a carry to get as much bonus IP as possible? How much IP do people usually get during double IP?