Sometimes one need to shift clock of subtitles. In the Gaupol software, from the top to the bottom, find first subtitle that is de-synced and following ones too. Then note its number.
Scroll down to find subtitle that is also de-synced and after which is a few seconds gap without subtitles.
click "Tools" / "Transform positions.."
Set time of the first and last subtitle and click Preview under each to verify correct adjustment.