Width property

Configures width to a fixed size, to grow as needed to display content, or to consume as much space as possible relative to other components, using weighting to influence size adjustments.

Setting Description
Script Layout Auto Sizing Auto-sizing configures the component to shrink or grow in accordance with its contents. For example, the width of a label can grow depending up on how much text it contains.
settings-sizing-stretch

Stretch allows a component to consume as much space as possible relative to other components, using weighting to influence size adjustments.

If two components are both set to stretch, they are both allocated 50% of the remaining space by default. This proportion can be adjusted by changing the weight value.

For example, if you set one component to a weight of 200, and the other to a weight of 100, then the first component occupies two thirds of the remaining space, while the other only takes one third. The first component appears twice the size of the other component, since its weight was two times the second component’s weight.
Script Layout Pixels Sets a fixed size in pixels. You can type an integer value into the box, or use up or down arrows to increment or decrement size. These arrows are visible when the component has focus.