The distribute functions will equalize space between the objects. Distribute won't give you a specific distance between objects unless you've carefully measure/divided the distance between the first and last object.
The Key Object really has little bearing on distribution distance. The Key Object won't be moved and all distribution will take place with that in mind.
Essentially the Distribute functions are not precision operations to gain a specified distance between objects in most instances.
If you require the objects to be the same and a specified distance apart here's a possible method to use...
- Draw one circle
- Select the circle with the Selection Tool (black arrow)
Effect > Distort & Transform > Transform
- Enter the distance you wish to have between circles in the
Move: Vertical field
- Enter the number of circles you wish to have in the
You should then have the number of circles you want at the specified intervals
CS6 screenshot, but the dialog is pretty much the same in newer versions, it merely looks a bit different.
To gain access to each circle as a individual objects you can "bake in" the effect by selecting the first circle again (if it's not still selected) and then choose
Object > Expand Appearance. This will create individual circles while removing the dynamic effect.
Another way is to...
- Draw one object
Object > Transform > Move and enter the distance desired
(or double-click the Selection Tool [black arrow] in the toolbar)
- Click the
Copy button in the dialog window.
- Then choose
Object > Transform > Transform Again to repeat the copy/move
(using the menu shortcut makes it faster --Command/Ctrl+d)
Just keep hitting the shortcut until you have the number of objects you want.