how do you find out where a ppm meter uses .5 or .7 conversion?

I have this one: http://www.waterfilters.net/HM-Digital-TDS-EZ-Water-Quality-Tester.html?zmam=91502559&zmas=3&zmac=4&zmap=HM-DIGITAL-TDS-EZ&gclid=CPq_6-rYtbwCFQxqfgodDjkAUw

that info. should be in the paper-work that came with the meter. it may be called tds factor....