STATSFEAR ANALYSIS: Scale of unstandardized residuals

Looking at the "Statsfear and Final Exam Score" output p.2 "Explore" the histograms of unstandardized residuals for both treatment groups, I want to make sure I am reading the x-axis correctly. Is the scale increasing by 1.33 units as you move from left to right?

In each of those histograms, four 'bins' can be found for every three units...so each bin represents 0.75 of a unit, and the four bins between, say, 0.0 and 3.0 represent:
0.0 - 0.75
0.75 - 1.50
1.50 - 2.25
2.25 - 3.00.