New user looking for a data dictionary or similar

Hello, I've been searching unsuccessfully for a resource that will give very specific definitions of fields. Below is just one example of the type of thing I'm trying to sort out.

Nothing adds up as expected (for example, if I have 7.7mm "white alone" and "6.0mm" "white alone, not hispanic" then I wouldn't expect the "Hispanic" to be as large as 3.9mm).

I'm sure it makes perfect sense but I can find anything that will explain how it does! Does anyone have a suggestion? Thanks

"Occupied housing units with a householder who is [one of the below]"
 Table ID   Table Title   TENURE BY UNITS IN STRUCTURE: Total: 
 B25032A   UNITS IN STRUCTURE (WHITE ALONE HOUSEHOLDER) 

                                                          7,763,068

 B25032G   UNITS IN STRUCTURE (TWO OR MORE RACES HOUSEHOLDER) 

                                                          1,071,433

 B25032H   UNITS IN STRUCTURE (WHITE ALONE, NOT HISPANIC OR LATINO HOUSEHOLDER) 

                                                          6,067,420

 B25032I   UNITS IN STRUCTURE (HISPANIC OR LATINO HOUSEHOLDER) 

                                                          3,981,701