A calendar question about custom repeats

Hi all,
I have a question regarding custom repeats on the iOS calendar.
I was delighted that this feature was introduced to iOS 8 and I think it hugely improves the app. The question I have is this: if I go to schedule a custom repeat, select the frequency as monthly and select a number with the “every” picker, I then have 2 options to select from. The “on the” allows me to select, say, the first Friday of the month and I understand that. But the “each,” selected by default, confuses me a little. Voiceover reads the grid of numbers but there appears to be no way to interact with it. My understanding is that with this screen, I could specify multiple dates each month, e.g. each 5th and 7th of the month. Tapping randomly does appear to add additional dates to each month but I don’t understand how or how to control it.
If this is an accessibility bug I would like to flag it to Apple but wonder if I’ve got it wrong somehow. Thanks for any clarification and apologies if this is addressed elsewhere (google searching didn’t turn up anything on Applevis).
I did find a tutorial that said there’s nothing you can do, but that doesn’t seem to add up to me.