Hi folks.
There is no need for any calculations to evenly distribute any number of copies around a full circle.
First, rotate the first copy by exactly 360°. Notice that, as you rotate and come back to the original position after going around one full circle, SketchUp will show 0° in the Measurement Toolbar. Don't take this as granted. Type 360 as the rotation angle. Validate this angle by a press of the Return key or the Enter key. Then, immediately enter the number of intervals, which, in this case of going around a full circle is also equal to the number of instances of the object, in the Measurement Toolbar. Again, press the Return or the Enter key to validate the value.
Done.
Be aware that the last copy will be superposed on the original. If this is raw geometry, it will merge with the original and there will be no problem of redundancy. However, if the object being copied is a group or a component, the copy will be superposed on the original but will be distinct. One of the two shall be deleted.
Just ideas.
Jean