What is the purpose of this purple dashed line area?

Does anyone know what this purple area represent?

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

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

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

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

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

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.