V3G: Cool, now do a balance to 100, record the number, disconnect and re-do the balance again. How much data got returned?
I re-did everything from scratch. Assuming that the (pre-paid) "balance to 100" / vodacom4me bundle remaining data is real-time:
On connecting, 8MB is reserved off my bundle (was 12 last week). Opening and closing several browser tabs/windows has no effect on my remaining bundle, even though netstat shows the number of active connections going up and down. There appears to be a high turnover of "active connections" eg once a page is loaded, if you wait a short time the connection will close and if you then refresh it will open a new active connection. If the billing system is really reserving a certain amount of data per connection, then it is 1) initially reserving sufficient for several simultaneous "active connections", and 2) probably re-using the unused portions.
On closing the HSDPA connection, about 6MB was returned.