Blitz with Face of the Mountain

While playing blitzcrank support, I find that when I buy Face of the Mountain, it shows 5 blue orbs instead of 4. The weird thing is, is that the 5th orb shows only when you have 4 charges and it stays underneath the 4th charge. When I looked at the enemy with Face of the Mountain, the 4 red orbs were there without a 5th one.