How to find correct education attainment information by zip-code

Hi all,

I would like to find education attainment information by zip-code nationwide via American Community Survey.

Since I am super new to the data, I wish to gain your perspective for two specific questions.

Using year 2016 as an example, the data file I download is "B15003  EDUCATIONAL ATTAINMENT".

B15003: Census Bureau Table

(1) How do I calculate the % of high school completion or higher correctly? There are something like estimate or margin values...

(2) In the file, it has ZCTA information. Should I use the below zipcode and ZCTA crosswork to get the the education attainment by zipcode?

https://udsmapper.org/zip-code-to-zcta-crosswalk/ 

Many thanks for your suggestion in advance.