I would call them, but I think all it means is that if you don't take and pass those classes by the time you matriculate, you can't go. I had a similar deal with Penn, for history and a drawing class. I took the history classes (hadn't finished by the time I applied so it showed up as a deficiency) because 3/5 of the schools I applied to required it. Took the drawing class over the summer and that was it. Unless I'm mistaken it means you are in as long as you pass those classes. Make sure you can find courses that are accepted by GSD and take them. The only thing I can think might be hard is getting the two history classes in one semester, unless there is an accelerated program somewhere.

there is a summer course for the two arch. history course that lasts for about two to three weeks. i'm not too worried about that. its the physics and calculus and i admit im a little embarrassed admitting this. my background was in social sciences and i haven't touch those subjects at all.

I don't think you should worry too much. Afterall, you generally only have to get a C or better - or sometimes just "Pass" - in these prerequisites to get them checked off. Where are you taking them? Frequently these courses are more bare-bones basic if you take them through a community college or city commuter-type school than if you take them in a larger university's summer program. But either way, if you're taking "intro" level course I don't think you need to worry about your undergrad major or whether you've ever touched these subjects. As long as you have the time to devote to them you should do ok (and not to scare you, but if you find you have huge troubles with passing basic physics in particular then you may find down the line that structures courses - and the structures exams on the arch. registration exam - are very difficult to get through.)

As far as what happens if you don't pass them: that depends on the M.Arch program and their current policies. One of my undergrad classmates failed physics the summer before he was supposed to enter a particular Ivy M.Arch program and was told he needed to defer his admission to the following year and pass it in the meantime (which he did). But I attended a different Ivy M.Arch program whose policy was usually that if someone had failed one pre-req then they could still enter the program but had to take that class as an elective on top of the usual course load in their first semester. I've heard of other programs even allowing the student to enter the program and pick up the pre-req the following summer.

If you decide to take Physics at Harvard Extension/Summer School, watch out. It's a bear! At least, for right-brained me it was. Harvard earned the nickname "Hard-vard."

There were also some GSD students taking it concurrently with their first semester there in the fall (I don't know if that's something that you have the option of doing).

I would think that Calculus would be equally difficult there. Good luck with the courseload!