Question about 2015-19 ACS

In the 2015-19 ACS - Table B25026 - one category for mover is "Estimated Total population in occupied housing units - owner occupied moved in 2017 or later"

If this is an accumulation of ACS data from 2015 to 2019, I don't see how this label applies to the respondents in the 2015 and 2016 survey?