ASA- LBR

[Chess Ref]

I am doing a 14U tourney this weekend. I need some re-educating on this particular SITCH.

R1 on 3b. batter gets a base on balls. Catcher thows back to pitcher who stands there. Batter rounds first base. At this point Batter-runner now has to immediately make a decision whether to go to 2B or return to 1b. Correct or is my thinking incorrect.

Bottom line is can Batter-runner round 1B then the LBR kicks in ?

Hope this is clear.I am clear in my head what I am asking but struggling to get it down clearly.