what are x-axis and y-axis labels in residual plots in stepwise regression?

I have generated histograms residual plots in stepwise regression. As per my understanding, the x-axis is residual and the y-axis is frequency. but my understanding seems wrong when I saw the plot as y-axis has a range from 0-0.25 and x-axis has ranged from -10 to 10. Please enlighten my knowledge in this regards. One of generated plot is attached.

[Greg Heath]

Those are not the values on the posted plot.

P.S. I find it easier to understand when both input and target are standardized to zero-mean/unit/variance

Greg