On a maps legend, what are the 2 measurements used for elevation?

The percentage of the school-aged population that receives special education and classified as having a learning disability for the year 2015 – 2016 is 3.5 percent of all students in public schools which is equivalent to 6.7 million, this is ages 3-21. among these students that receive special education services and having specific learning disabilities is 3.4 percent.