Where the system updates get installed in HTC explorer?

I am seeing a message on my taskbar System updates are available. When I am tapping to that message it is showing some 29 MB updates. I am running sort of internal memory, so every-time I am postponing the updates to later(I think it will consume 29 MB internal memory). Is this true that on installing the updates will consume internal memory? I am using HTC explorer having gingerbread(2.3) version of Android.