We are limited on how much data we can import per day according to your Salesforce API limit. You can check your API limit by following this guide.
If we reach the API limit during the import, we will automatically resume the import where we left off as soon as the limit is refreshed each day.
You also have a storage limit in Salesforce, which may impact our ability to import all data for you. Please check the "Storage Capacity Limits" section of the Salesforce manual to check your plan's limits.