Objectscale command is used to add or removes supported scales for annotative objects.
How to access OBJECTSCALE
We can double-click the viewport and then find Annotation tab > Annotation Scaling panel > OBJECTSCALE, shown as below,
Then select annotated objects and press Enter key to pop up the Annotated Object Scale dialog box where you can delete the object scales from the list,
Then we can add the current annotation scale to annotative objects manually by clicking the “Add Current Scale” button, shown as below,
Then select annotative objects as prompted, then press Enter key.
You can repeat this command and add current scale to other viewport, after all this, you’ll see that the annotative dimension text in the same size.
Check the video to see all the steps: