Content Search export

Hello!
Thank you for reaching out. 
There is a great article published by Microsoft that explains why you might see different figures when it comes to estimated and the actual eDiscovery results. I am sharing a link here for your perusal. I hope this helps to clarify why it happens 
Link to Documentation:  Estimated and actual eDiscovery search results | Microsoft Learn

Please mark the answer as solution if it serves to explain why this issue occurs for the benefit of the rest of the community. Thank you!