The way the rolling windows work on our Uncapped product is as follows:
Start of Uncapped service:
Day 1 = 6gb
Day 2 = 1gb
Day 3 = 1gb
Day 4 = 2gb
Day 5 = 1gb
Day 6 = 2gb
Day 7 = 1gb
Total: 14gb
After the first 7 days we calculate your usage for the last 7 days. Meaning that your next 7 days will be calculated from Day 2 to Day 8 and the next will be from Day 3 to Day 9, if this makes sense. So if we use above example, since you downloaded 8gb from Day 2 to Day 7 you will be can to download roughly 6gb to play with for Day 2 to Day 8. Bearing in mind if you do use that 6gb on Day 8 you will only have 1gb for period Day 3 to Day 9 since your total usage for period Day 2 to Day 8 was 13gb.
You can also look at our KB article for more information on the service:
http://kb.webafrica.co.za/article/AA-00833/33/Internet-Connectivity/ADSL/Home-Uncapped-QA.html.