Fortify Enchanting potions not working?

I'm playing Special Edition on PS4 and just trying to enchant a better set of gear. When I go to enchant something without a potion, it'll let me do something like +15% sneak. I take the fortify enchanting potion. Enchanting menu shows I can do +20% sneak if I use a grand soul, so I do. Go to check the item in my inventory, and it is at the regular +15% it would have been without the potion, no improvement at all.

I'm not trying to exploit anything, have no mods installed. Has anyone else dealt with this? I've tried it a few times, on different items, and it still doesn't seem to be working properly.