CGPA to Percentage Conversion

I've heard that our college's CGPA to Percentage(%) conversion of grade is done as :

Percentage = ( CGPA - 0.5 ) x 10

example : 8.5 CGPA => 80%

Can any passed out student vouch for it and can someone tell me, do we get a Percentage(%) of our grade on the final certificate ? (all sems combined)