What does the PIT function return?

[adrianbeer]

Hello, after fitting a model I tried to plot the PIT this way:

pit <- PIT(msgarch.fit.ml, do.its=TRUE)
hist(pit, breaks="Scott")

which returned the image below.

I don't quite understand what is displayed here. To my knowledge the PIT should be bounded between 0 and 1 (on the x-axis) and contain the values $$F(y_t|\mathcal{I}_{t-1}, \hat\Psi)$$ for all observations y and cdf F, s.t. the quantity is ideally uniformly distributed. E.g.:

So what exactly is displayed in the graph?