1DOT2 15 Minutes Wall-Mounted Rotating Sauna Hourglass Timer,White Sand,Accurate in Counting time,Slight Error, not Blocked

the sand is actually around 15mins worth (14.5) but the markers don't correlate at all to 5 10 or 15 mins as the sand begins way above the 15min marker.Counting time is the job of this thing so its pretty rubbish.