How to change default reminder time for multiple entries...

Hopefully someone already knows and I've not read the FAQ's properly but, how do I update a list of events to remind me at a specific time?

For example I have scheduled a dinner at one time and then a show later that same day.
If I scheduled one only I get a reply from Sandy saying:

I have scheduled:

#1 12:00pm Dinner
- Email reminder at 11:00am

To that I can reply

Sandy remind me at 10:00am

and she'll update the email reminder time...BUT, if I schedule more than one appointment in the email and get back:

I have scheduled:

#1 12:00pm Dinner
- Email reminder at 11:00am

#2 14:30pm Show
- Email reminder at 13:30pm

...and send the same "remind me at 10:30am" update I receive:

I scheduled:

#1 10:30am Re
- Email reminder at 9:30am

Which basically ignores the original Dinner appointment and schedules Re and sets a reminder time 1 hour (my default reminder time) before the reminder I wanted.

I'm sure it's obvious...but what am I doing wrong?

I have tried:

Sandy remind me of #1 at 10:30am

But that only scheduled:

#1 10:30am #1
- Email reminder at 9:30am

Which is actually, when I looked at it, what should happen...so I’m stumped.