sql server – Hourly Transaction Log files size not consistent – is this Differential backup file?

I am new to DBA task here.

I am trying to restore database with transactional logs (in SQB file format) that our company get 24 times each hour daily thru FTP site, and then I have to convert them to BAK file format using “RedGate’s SQL Backup” application.

Then, I am planning to restore each transactional log with “NoRecovery” as we would have to restore each hour.

I found there is a pattern of file number “..04” which is really big compared to other hourly transactional logs.

I did not get specific instruction regards to this file “..04” from the vendor’s documentation who provides data.

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I am curious whether I should treat this particular file as a regular transactional log or is this like “differential backup file” that I have treat it differently?