Hi, please help me understand how trial works.

I had small service running for several days, consuming minimal resources (30 mb ram, almost 0 cpu and network). Yesterday I checked I had 4$+ remaining. I didn't apply changes. Afaik, trial works until balance positive.

This evening, I logged in with a message: "Your Trial has Expired"
"Thanks for trying Railway! Choose a plan to continue using the platform."

Is there time limits for Trial or anything like that?

I checked Usage, but see only Current Usage $0.14. I.e nothing that could exhaust remaining trial balance.