I'm importing a list of leads with emails, 323 total. Only 309 are showing as populating the list created. Why are not all importing?
Agree with Jamie, it's probably duplicate records in your list.
I recommend always cleaning up a spreadsheet before uploading it into Marketo, here is a good tutorial on several ways how to deal with duplicate entires in Excel - How to Merge Data in Duplicate Rows in Excel : Microsoft Excel Tips - YouTube
Besides Dupes which might have been on the list, perhaps there were some invalid email address that were just skipped over?
Lastly, are you sure you're viewing the results of the Static List you imported?