Use TTS SSML. I use it with the Fully Kiosk Browser Controller. Scroll down, the SSML info is near the end of the first post that also documents why {} instead of <>
I do not recommend an entry countdown, gives a thief too much information.
This is my Exit Delay countdown
{speak}Alarm system is arming in 30 seconds, please exit the facility. {break time=“1s”/} 25 seconds{break time=“2800ms”/}20 seconds{break time=“2800ms”/}15 seconds{break time=“2800ms”/}10 seconds{break time=“2800ms”/}5{break time=“700ms”/}4{break time=“700ms”/}3{break time=“700ms”/}2{break time=“700ms”/}1{/speak}
My Entry delay TTS
Disarm system, or police will arrive shortly
BTW Countdowns are problematic on ST due to cloud and internet delays. It works well on my local Hubitat system.