Any engineers on board? Zero on the shot clock, no horn

[pizanno]

1) I start the shot clock. NCAA womens 30 sec shot clock.
2) Shot clock runs, but display still indicates 30.
3) I deduce this to mean "30" on the shot clock means 29.1 to 30.0 in actual time
OR:
"30" = 29.1 to 30.0
"29" = 28.1 to 29.0
"28" = 27.1 to 28.0
..and so on until:
"2" = 1.1 to 2.0
"1" = 0.1 to 1.0

So: how is "0" on the shot clock possible without a horn?

My brain tels me if we had zero on the shot clock, this must mean:

"0" = 0.1 to 0.9
"1" = 1.0 to 1.9
...and so on until:
"28" = 28.0 to 28.9
"29" = 29.0 to 29.9
which means:
"30" = 30.0 to 30.9 ?!!!

Does this make sense? Again, there was a delay from starting the shot clock to when the 30 changes to 29.