So - let's say you upload 221 and 198 are "acquired". Acquired means that they are a new person/lead in your database when you upload the list. This means that 23 leads were already in your database and Marketo deduped against them on list import, so they were not acquired by this list import.
Reasons for the discrepancy between 231 on the list and 221 uploaded could be there were duplicates names/emails on the import list (these would only be imported once), or there were some errors in the email addresses on upload, so the lead was skipped on upload. If you put an email address in for a report when uploading lists, Marketo sends you an email that outlines any errors that occurred.