No.
The Screenshot should make it clearer.
Its a test setup; there is only one truck station, one city and one supply depot lvl 3.
The depot should add 100 extension points, yet it only adds 10 as shown in the screenshot.
Extension points from supply bases do not give the extension points they should give. I tried in both builds, and the amount of points they give varies. Upgrades do not seem to influence this either. A supply base lvl 3 gives the same 10 extension points as a supply base lvl 1.