Same H20,2 Dif. Tests, 2 Dif Results?

Ok so I just calibrated my new milwaukee ph pen meter with 4.01 and 7.01 sloution as directed and then tested my RO'd water and the results were 3.0..with my ph drops from general hydroponics - tested same water..and results were 6.5...what could be the problem here?

re calibrate the pen and if still having a problem call milwaukee and explain to them