Brewing Stand Ingredients Stop Brewing When Half-Stack Clicked

I accidentally placed 2 pieces of Glowstone into the Brewing Stand. When I realized I had put too much, I riht-clicked to take out half of the stack, thus leaving one. However, when I did this, one was left in (like normal), but the brewing process reset and stopped. When I clicked on the glowstone in the stand, it just jumped into my inventory. (Keep in mind that I wasn't shift-clicking)