It's not a lot, most studies are misleading and "health experts" recommend 400iu a day which is a joke and anymore than 4000iu is "dangerous". Same with Vit C, they say 50mg is enough but yet 1000mg has been proven to strengthen immune system and help with a cold.
A lot of these studies for all vitamins are done on bed ridden older people in hospitals, that's where the %DV*/NRV%* (daily recommended) comes from if you look at the back of supplements.
I take 8000iu separately and my multivitamin has an extra 5000iu, you don't need to take 13000iu, 5000-10000 is safe and you get the full benefits, long term use I have more energy, I sleep better, bones don't hurt, overall mood is better.
I take multivitamin vitamins and supplements from bodybuilding companies because they dose everything high so you get the full benefits while still being safe, I use Orange Triad as it has everything, as you can see the doses are much higher than the %DV* (which is from older bed ridden people and doesn't help a young active person).