The regression function has:
r^2=0.54
This indicates a moderate fit, not a strong fit. The model explains some of the variation in the data, but not as strongly as a model with an r^2value closer to 1.
Now consider the prediction at:
x=20.6
From the scatterplot, the observed data values extend to about:
x=18
The prediction at x=20.6is beyond the observed data, so it is an extrapolation. However, it is not very far beyond the data range.
Because x=20.6is within a reasonable extrapolation range and the model has a moderate fit, the prediction is appropriate.