Just got a reply from Steve Shaw on this.
As per rule 3-2-4-a, the game clock shall not display tenths of seconds. This should be corrected in the pregame if we see the tenths of seconds displayed – and is a simple software setting in the clock system. The reason behind this is that we don’t want players and officials having to interpolate end of game situations like the minimum time required to spike a ball etc.
As per the convention of the clocks, if tenths of seconds are not displayed, the clock will go to 0:00 when there is truly no time remaining. So, if the tenths of a second clock displays 0.9, the game clock still displays 0:01. It is still at 0:01 when the tenths would be at 0.1. Likewise, when the clock displays 0:03, internal timing and tenths of a second would display 2.9 down through 2.1. This would be confusing to the QB and officials as to the allowance of spiking the ball.
The bottom line is to get the clock corrected before we start, and certainly before we get to the 2nd or 4th quarters. In your question, if the clock in tenths displayed 0.4, the proper clock would display 0:01, and stay at 0:01through the display of 0.1 in tenths. When the tenths went to 0.0 the normal clock would display 0:00.
Steve Shaw
CFO National Coordinator of Football Officials
Secretary-Rules Editor, NCAA Football Rules Committee