What are the green numbers beside the items in smite ? i don't think so they are any amount of currency or an amount of power the god will deal.
Some items have stacks. (Book of Thoth, Warlock's Sash, etc.) The number on the item you're using is the amount of stacks it currently has. The items do have a cap limit. Check the details and passives of that item to see what it does.
From Smite Wiki about Book of Thoth:
"PASSIVE: You permanently gain 10 Mana per Stack, and receive 5 Stacks for a god kill, and 1 Stack for a minion kill (max. 75 Stacks). Additionally, 3% of your Mana is converted to Magical Power."