You may want to know which Salesforce fields a specific Marketo field is tied to as shown in this document. You will be able to see that the mappings are either not update or a few fields are missing that were created recently.
The Field Mapping that you are seeing under Admin -> Salesforce, as well as the mappings included on that export, are a historical log of how the mappings were set when the SFDC integration was originally implemented. Unfortunately, that page does not refresh when new fields are added, or when mappings are changed. We don't have any other tool that would allow us to export all of the field mappings in your instance as they are currently set either, so the best workaround for this is to check each of your fields within Admin -> Field Management.
There is an idea in the Marketo Community specifically asking for this feature to be added and we would recommend that you add your vote to that so our product team sees that there is interest in getting this functionality added to Marketo in a future release.