To be more specific, the 'optional' KB2952664 was published June 9th, 2015. The 'Recommended' KB2952664 was published today. Microsoft has prior history of re-releasing the same KB numbers at different times as they update the fixes but for some reason released both of them at the same time today.
@ schmidthouse, lucD,
Yes, messed up. I'm seeing the same, a 25KB update for both after one or the other full 6.0 MB is installed. Records for installation is now up to seven KB2952664 in installed updates; all were successful. I uninstalled both and tried installing the June 9th one first, but it did not matter. Same result either way. Uninstalling did not remove any entries in installed update logs so the count just keeps going up.
-midnight,
I'd leave this one alone until someone reports this update is working as it should. I suspect the way it should have went was by having the 'Recommended' update automatically remove the optional version and then automatically installing itself as the newest update. Which is likely what the 25KB file is for.