What do the values for Get-MailboxStatistics for Exchange 2013 mean?

vivekk9 used Ask the Experts™
I ran the following command on Exchange 2013 and got the output,

[PS] C:\Windows\system32>Get-MailboxStatistics -Identity mschmidt | select name, *size*

name                         :
TotalDeletedItemSize         : 143.4 MB (150,352,426 bytes)
TotalItemSize                : 3.212 GB (3,448,551,942 bytes)

MessageTableTotalSize        : 825.2 MB (865,239,040 bytes)
MessageTableAvailableSize    : 21.28 MB (22,315,008 bytes)
AttachmentTableTotalSize     : 2.202 GB (2,364,768,256 bytes)
AttachmentTableAvailableSize : 10.53 MB (11,042,816 bytes)
OtherTablesTotalSize         : 49.09 MB (51,478,528 bytes)
OtherTablesAvailableSize     : 2.094 MB (2,195,456 bytes)

I know what TotalDeleltedItemSize and TotalItemSize mean. Can anyone tell me what the other values (in bold) mean?

Also, in this case the total Mailbox size is = TotalItemSize or the addition of all the other values too?
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SaberSupport Escalation Engineer
Those are database table entries.

Messages have their own table in the database.

MessageTableTotalSize       All messages for this mailbox are taking up this much space.
MessageTableAvailableSize    Message Table space currently available.
AttachmentTableTotalSize     Message Table allocated space for this user.
AttachmentTableAvailableSize Space allotted for message attachments.
OtherTablesTotalSize         Other tables total size, (Calendars, contacts, etc.)
OtherTablesAvailableSize    Calendars, contacts available space remaining.
IT Engineer
Distinguished Expert 2017
Mailbox is like SQL database.
All records are stored in one row with different tables.
All tables size combine together = MailboxSize

This is example of my datastore



Thank you Saber and Tom. This information is great help and the exact explanation I was looking for.

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