I will immediately verbalize, "Batter is out!" because it's no different than any other situation where the batter/BR is immediately out.
If the batter tries to run for first, I will verbalize, "She's out! She's out! She's still out!"
Oddly, U3K is not covered in the 2024-2025 NFHS softball umpires manual
. I just checked there to see if there was an authorized or approved mechanic.
I think saying nothing when the batter is immediately out on a U3K can lead to needless confusion and chaos, especially with many coaches instructing their girls to run on
any U3K scenario - even when they are immediately out by rule.