Header Database Compaction question

This is mostly out of curiosity, not really any sort of issue.
I am wondering why, when I compact databases, some empty groups show a size of 122.9 KB while others show a size of 184.3 KB?
Just wondering.
I am wondering why, when I compact databases, some empty groups show a size of 122.9 KB while others show a size of 184.3 KB?
Just wondering.