A subtitle tracked for a 24fps Blu-ray rip will drift out of sync if you are watching a 25fps web-dl streaming version. Step-by-Step: How to Download the Correct SRT File

You searched for – and you’ve come to the right place.

Let's get to the core of the fix. The "upd" likely means you need to update or fix your subtitle process. Here’s how to do it.

However, based on the terms, here’s what you’re likely looking for:

If the subtitles are consistently ahead or behind by a fixed amount: