I found this in the Black Clouds & Silver Linings - Dream Theater Guitar Tab Book. The notation implies a harmonic on the second and third strings, but what do 2.7 and 3.2 mean?
I believe that this is referring to where you would place your finger to get the desired harmonics. The harmonic that generates the major third is right before the 4th fret, which would be 3.85. 3.2 would be a harmonic near just beyond the 3rd fret, which should give you a D on the G string. This picture outlines the placement of the harmonics and the decimal representation for some of them. Looking at the harmonic that shows not in parentheses in your example, the image doesn't match decimal-wise but you can see that the note that corresponds is the same.