Heey Manish,
Is this document type object newly created? Cause when i take a look at your screenshot i see that the old value is "” so it was either empty or not yet there and the new value is ‘com.mendix.basis etc. The old value in this case being the attribute contents of the entitiy. Maybe also worth checking is what the LogType on the Log entity associated with this LogLine is.
Kind regards,
Edo