Supply barrels on any given server refill in 30-minute intervals however this is different on every server. If you plan on a longer session you can use this tool to narrow down this point in increments for the server you are currently on.

1. , set marker (you just opened a barrel and know its contents)
2. 0 you checked the barrel again, nothing changed (marks the section from last marker as red, also updates the marker)
3. you checked and refresh happened (marks the section from last marker as green, also updates the marker)
4. You now have two green windows that you can further narrow down with steps 1-3
5. reset everything