When the OP says that they did indeed put the .3 on the clock, this tells us that his best impression was 5.3 at the start of the count. Consider this, if there is a "normal" discrepancy between the whistle and the stoppage of the clock, there should be even less time left. Lag/reaction time is normal. Stopping the clock early in anticipation of the violation is unacceptable. One can only assume that he checked with the timer to be sure that the clock did stop before the whistle. If the answer is no, as you say, I don't see a lot of alternative but to say "Oh my gosh, my counting is abysmal!" and proceed from there.

I checked the clock WHEN I started my count. I saw 5.3. I counted to 5 and blew my whistle at which point we realized the clock had stopped prematurely.

Good job.

Clock glance.
 

Great job.

Exactly what you are supposed to do.

I want to know how u saw exactly 5.3 on a running clock. That's amazing!

For approximately .1 second the clock says 5.3, are you honestly saying you have never seen any digit in the .1 second it was on the clock? Is it just a blur when you look at the tenths digit when its running?

2 years in a row HS crews in Virginia have allowed catch and shoot to win games with 0.3 or less on the clock.

Very, very sad. It's a rule that actually makes our lives easier and yet some of us still manage to mess it up.

No, I can see the digits quickly scrolling by.... Signals from the eye take about a tenth of a second to reach the brain. The blink of an eye is approximately two tenths of a second. When I go from looking away at my running timer on my phone and then glance at it, I can pinpoint it to a small range (maybe within .3 seconds), but I can't tell you exactly to the tenth of a second. The official has to see that the ball is at the disposal of the inbounder, glance at the running clock, and start the count. To say for certain it was exactly at 5.3 is not humanly possible. If his brain registers 5.3, then it was at least 5.4. That's the only point I'm trying to make. I would still ask the table when they stopped the clock, and not immediately go to 0.3.

They stopped it at 1.6 seconds. ;)

:) I know. 1.6 is weird, right? I think maybe they stopped it after the basket by mistake at 5.3, that is why the official is so adamant he saw exactly 5.3, and then the timer said oops, i wasn't supposed to stop it, and started it again, and then stopped it on his 5-second count whistle. I would like to hear more of the conversation with the table.

(from Wikipedia)
The human eye and its brain interface, the human visual system, can process 10 to 12 separate images per second, perceiving them individually.

[1] The threshold of human visual perception varies depending on what is being measured. When looking at a lighted display, people begin to notice a brief interruption of darkness if it is about 16 milliseconds or longer.

[2] Observers can recall one specific image in an unbroken series of different images, each of which lasts as little as 13 milliseconds.

Coach, it seems the ascertion regarding 10-12 visual images processed per second by a human brain, is modified by element [2], which explains why/how it is possible to perceive the presentation of individual tenths on the clock.

I also think (no scientific evidence) that there's a difference between the lighted segments / light bulbs on a stadium clock and the lcds used on a phone in terms of being able to see individual digits.

Any newspaper or internet story on this incident? BTW, this same thing happened in So Cal in playoffs last year and ended the team's season!!