Unwrapping Issues

I have been searching for a solution to a problem I am encountering while unwrapping and haven’t been able to find a solution. Possibly due to not knowing if their is a specific term to the problem.

Anyways when I unwrapping portions of my project some of them are in the wrong place and I am not sure what is causing this and how to correct it. Below is screenshot of the issue I am having. On the right is a arm model I am using. When I unwrap it some of the vertices are spread out while other parts are bunched up.

I have altered seams, deleted and remade faces, edges and vertices and the problem still exists. So what is causing this and how to I address it?

Without a sample of your file, it’s hard to say. Did you mark a seam before unwrapping?

Classic. You need a seam running down the length of the shape. Put one on the underside where it will be least noticeable.

Edit: Picture to illustrate