## Summary
* **What is the goal of this PR?**
Resolve [KoSync progress does not sync between Crosspoint-reader and
KOReader
(Kindle)](https://github.com/crosspoint-reader/crosspoint-reader/issues/502)
* **What changes are included?**
KOReaderDocumentId::getOffset() - Update the value for the md5 offset
calculation to match KOReader.
## Additional Context
I've tested this with a couple of my ebooks and binary matching with
KOReader sync seems to be working fine now for both pushing and pulling
progress.
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### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _**NO**_
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