The revision cloud arc length by default is set and will reset after you save the drawing and close it. To have a consistent revision cloud tool it is best to modify the revision tool on the tool palettes.
How to modify the Revision Cloud Tool on the tool palette:
You can use the tool that is on the Documents palette on the Annotation tab. Make sure you right click on the tool and make a copy of it so you are not overwriting the out of box tool.
Or you can drag and drop a Revision cloud from the Content Browser. To open this just type CONTENTBROWSER at the command line.
Click on Documentation Tool Catalog - Imperial or Metric.
Click on the i-dropper icon and hold. The pen will fill up and then you can drag the curser over to the tool palette and release the left mouse button to add it to the tools.
To modify the arch length right click on the tool on the tool palette and click on properties.
Within the Tool Properties dialog box change the size of the "Arc Length"