I have just recently downloaded the newest version of Minecraft Forge, 1.10. so, i created new survival world and gave myself a bonus chest. I broke the chest open and i collected the items. When i opened my inventory, i noticed that the single stone pickax and one wooden ax had manged to multiply to fill up the rest of my space in my inventory. Although this is sort of helpful, i assume this is not supposed to happen. Afterwards i went back afterwards to make sure that Minecraft itself had made a glitch in its new update but it did not happen in my normal Minecraft account. Hope this is an easy fix!