I'm confused with the suicide burn countdown timer

Hi All,

I'm confused by the KER landing suicide burn count down timer.

I was assuming that when that timer reaches zero and you start a full throttle retrograde burn you just reach zero velocity before touch down. I also assumed this was the most efficient landing.

However, when I start my burn at t=0, the suicide timer quickly starts to increase again. Within a few seconds it's at 30 seconds, so I kill the engine, and wait for it to reach zero again, start the burn, etc.

This way I'm able to land, but it does not make sense. Can somebody explain?