Smelting time refreshed

Don't know if it works for other fuel sources, but In my specific instance I started smelting clay into bricks using lava buckets and four seperate furnaces, and when it was around halfway done I went to the nether and came back. The timer to show how long until the fuel ran out completely refreshed to full.

UPDATE: Seems to be just a visual glitch, as the timer showed as full up until the fuel ran out.