Q:

Why is more than one spectral line created on the de ecxitiation of a hydrogen atom

When an electron is de excited from a higher energy level to a lower one only one lone fits the bill then why is it that so many lines are created example n=4 to n=1 

A:

If you're talking about what I think you are (and if you're not I will delete this answer) but what you mean by "one lone fits the bill" is only 1 energy value represents the drop from n=4 to n=1. However, Hydrogen's electron has many jumps that it can make. It can drop from n=4 to n=3 or n=2 or n=1. It doesn't even have to start at n=4 it can start at n=3 and drop to n=2 and n=1, and it can start at n=2 and drop to n=1. While it is true each movement of an electron (from one energy level to another) will only produce a certain amount of energy for that jump, there are many jumps Hydrogen can make, resulting in the multiple lines you see on an absorption/emission spectrum.
Also note this question may also answer your question

