number to gpa calculation, common dataset vs collegeboard?

Hi,

this link to the collegboard converts number grades to a 4.0 based gpa:
http://www.collegeboard.com/html/academicTracker-howtoconvert.html

there’s a big difference in achievement between a 93 and a 100 yet the collegboard conversion chart calls both grades 4.0. My questions are:

  • how do colleges convert number grades to a 4.0 based gpa for the common dataset?
  • is there another conversion scale we should be using when comparing number grades to grades reported in cds?

tia,