What is the geometric meaning of $\frac{c\cdot n}{p\cdot n}-1$, for $c$ a point on a plane, $n$ a unit normal, and $p$ some other point?

Question

I'm trying to understand some piece of code and have the following expression:

Dot(c,n)/Dot(p,n) - 1.0

representing $$\frac{c\cdot n}{p\cdot n}-1$$

where $c$ is a point on the plane, $n$ is the (normalized) plane normal, $p$ is some other point that is not on the plane. Dot is a function that returns the dot product between the two arguments passed to it.

I think it's got something to do with the distance of $p$ to the plane, but I can't quite figure out what the exact geometrical meaning of this expression is.

Can someone help?