What is the meaning of $c - i \infty$?

Question

I was reading this page on wikipedia and I'm confused with a notation that they used. I'm familiar with the idia of a complex infinity: It's an infinite number with an unknown argument, so I like to think of it like: $\tilde{\infty} = \infty e^{i\varphi}$, for some $\varphi \in ]-\pi,\pi]$.

But, in this wikipedia page they use write: $c - i \infty$. What does this mean? It's not the complex infinity I think, as $\lim_{a\to\infty}\arg(c - i a)=\lim_{a\to\infty} \arctan(- a/c) = -\pi/2$ and so the argument is not unknown.

Answer 1

Below the table on the Wikpedia page:

In the limits of integration for the inverse transform, c is a constant which depends on the nature of the transform function. For example, for the one and two-sided Laplace transform, c must be greater than the largest real part of the zeroes of the transform function.

As an example, the inverse Laplace transformation has an integral from $c - iT$ to $c + iT$ (a vertical segment in the complex plane) with $T \to \infty$, where $c$ is as described above.