Please help us help you and fill where relevant:
LimeSurvey version: 6.10.6
Own server or LimeSurvey Cloud:LimeSurvey Cloud
Survey theme/template:Bootswatch
================= have read this, but I still don't quite know how to hide the countdown timer.

I'd really appreciate it if you could teach me. Thank you! www.limesurvey.org/manual/Question_type_-_Text_display#Timer