Komen Fullfail

I think the 4th Orb Puzzle is wrong/bugged? Apple + Apple = 10 so Apple is 5, Apple + Banana = 15 resulting in Banana being 10 Banana x Mango = 20 so Mango is 2. Apple + Mango - Banana = 5 + 2 - 10 = 7 - 12 = -5 but the answer that let me progress the game was -3