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Each of the three wired inserters below are highlighted yellow in their respective pictures. They also come in the same sequence as it occurs.
U235 and U238 exiting from the centrifuge are held in the chest red wired to inserter one. Once there is 41 U235 this first inserter takes 1 U235.

Check override stack size, then change the stack size in the field for it, then click on set stack size. In order varying to this it may not allow you to change the stack to one.

The one piece of U235 taken by the first inserter triggers inserter two.
Inserter two wont work until there is 1 U235 taken by inserter one. It removes the 40 U235 that then go back in the centrifuge for another cycle.
The third inserter (note the green wire here) tallies both chests and when there is only one U235 in both chests (when inserter two is finished) it removes that one and thus turns itself and inserter two back off in effect resetting the system.