is a setting that is saved with model space, layout viewports, and model views. When you add objects to your drawing, they support the current annotation scale and are scaled based on that scale setting and automatically displayed at the correct size in model space.
Before you add annotative objects to your model, you set the annotation scale. Think about the eventual scale settings of the viewports in which the annotations will display. The annotation scale should be set to the same scale as the viewport in which the annotative objects will display in the layout (or the plot scale if plotting from model space). For example, if the annotative objects will display in a viewport that has a scale of 1:2, then you set the annotation scale to 1:2.
When working on the model tab or when a viewport is selected, the current annotation scale is displayed on the application or drawing status bar. You can use the status bars to change the annotation scale.
You can use the system variable to update annotative objects to support the current scale automatically when the annotation scale is changed. ANNOAUTOSCALE is turned off by default to keep file size down and improve performance. When ANNOAUTOSCALE is off, this button is displayed this way on the right side of the drawing status bar or application status bar.
Use the system variable to set a default annotation scale setting.