The email size in Veritas Alta Archiving Personal Archive (PA) is larger/smaller when restored locally.
Example:
In PA, the size is seen as 95MB even though the attachment is 72MB:

After this message is restored locally it shows the original size of roughly 72MB:

This is expected behavior because Veritas Alta Archiving stores emails in .EML format on Azure blob storage, and it's this size that is shown in the PA GUI. When a message is restored it gets retrieved in its native format as a .MSG which will be smaller than what is shown in PA.
The size will be compressed/increased depending on the format type being archived.