They should of made the vault like the equipment page on the pause menu; hover over primary weapon icon and it shows you say, 12 or 18 just like the menu. That way you can store 18 of each type without it pushing past the "limits". And do the same for inventory, just hover over general, brings up upgrade mats, and again, the same for consumables, voila, there's all your synths and glimmer boosters. Problem solved