What is the purpose of this purple dashed line area?

Question

Does anyone know what this purple area represent?

Answer 1

It shows the available space where text can be expanded.

You can see this dashed area after text which means it is area where text can be expanded.

Let me show an example with just one character:

And an example with more characters looks like this. It can be seen that length of purple dashed line area is decreased:

It is possible to run the following code snippent and open dev tools to see this purple dashed area:

*, html, body {
    box-sizing: border-box;
    margin: 0;
}

div {
    position: relative;
    background-color: lightgreen;
}

button {
  display: flex;
  width: 100px;
}

<div>
    <button>1</button>
</div>

Answer 2

It is white space. For example you have a container with 100% of width and two divs inside, one of those with 50% and another width 40% of width, it means that there is 10% of space empty... this 10% would be shown in this purple dashed line area by the Google inspector.