When $f\left(x\right)=0$, the number is $-\frac{19}{4}$.

When the number is $0$,  $f\left(x\right)=19$.

The value of $f\left(x\right)$ increases by $1$ for each increase of $4$ in the value of the number.

For each increase of $1$ in the value of the number, $f\left(x\right)$ increases by $4$.