2010-2014 ACS sample size


I am attempting to work fith data from the 2010-2014 5 year ACS. Downloading the extract from the IPUMS site I notice a total sample size of 15,552,144, while the technical documentation from teh ACS states a sample size of 15,719,324; after subtracting the Puerto Rico Community responses, I am still left with 15,636,088. Can you please explain the discrepancy? The source I am referencing is page 1 of the following document: