Different Number of Container Elements

Why is the number of elements of a container different after the update from 2033 to 2034 / 2034 SP1?

Up to and including version 2033 the displayed number was determined from the full text index.
This had the following effects for mails, which were delivered for several recipients also several times:
If a mail, which is addressed to several recipients, was delivered individually by the sending mail server,
then this mail was counted multiple times in the full-text index, because it is also indexed with each new delivery.
In the data part of the archive container, however, the mail was overwritten in each case, and is therefore only present once.
I.e. if a mail went to 3 recipients, and was delivered in each case individually, then as number 3 was indicated, because 3 mails were indexed.
However, if the archive container was re-indexed at a later time, then 1 was displayed as the number.
Because the mail only exists once in the data container, and was therefore only indexed once when it was re-indexed.
With version 2034 this was changed:
When migrating the archive container, the number of mails is stored in the data part, and kept there continuously.
The display of the mails corresponds therefore to the mails which are stored in the data container.
Therefore, in most cases, the displayed number of mails after the update to version 2034 will be smaller than before the update.
The same applies to versions before 2034 in case an archive container was re-indexed.