Thank you for posting your question on History Hub!
No, the number of digitized documents does not include all of the documents that Ancestry and FamilySearch are showing. It will always be different because NARA is putting online the documents that are only in our possession, while Ancestry and FamilySearch are only putting the digitized copies online of the specific records that they work with us on, and by using source material that they have found in other archives, historical institutions, etc. As such there are digitized records accessible from some of our partners that we are not showing in our search results because they are not our records. There are also countless records that we have scanned and put online that users will not find on Ancestry or FamilySearch as we did not partner with them on those scanning projects.
You may wish to share with your Club NARA’s Resources for Genealogists, as well as the History Hub Blog titled Suggestions and Advice for Family History Researchers. Also, the FamilySearch Research wiki for United States Genealogy may be useful.
We hope this information is helpful and best of luck with your research!