Display of minion kills is sometimes wrong for enemy junglers

I had noticed this bug couple times already. It is pretty sad I don't have any pics or videos to prove it. If anyone had experienced the same thing as I did. Please comment!

So this bug isn't influencing the game at all. It is a display bug. But it sometimes make people confuse. So sometimes I had noticed the enemy jungler had farmed, for example, 20 monsters. This data should be showed on the score board till he show up next time and this data would update. However, sometimes when the jungler left lane, the minion kills number displayed on the score board would decrease!!!! Usually down to 6 or 7. This is pretty confusing. I had met bug this several times.

My English is not that good so I hope I explained the bug well!