The only thing I don't care for about percentages is they really don't tell us what kind of volumes we are talking about. I would imagine that RIM and Symbian didn't lose 80% of their current user base but rather the number of devices has still climbed significantly.
IE if Rim had 1M phones, and they lost 20% they would still have 800K devices, but if the market increased by 20% in order to remain at the same level they would need 1.2M devices.
On the flip side the 4.1% likely understates the number of WP that they are increasing by. If they had 1M phones before, they increased that number by 50% or 1.5M. If they market grew 20% the actual number of devices is now 1.8M. so really they would have actually increased by 80% (numbers I've seen is it's roughly 2x increase year over year)
iOS probably held fairly steady and didn't increase the number of devices by much, but didn't lose any subscribers either. Then obviously android saw large gains in total number of devices. 5% increase in a market that grew 20% is actually a huge increase in device numbers. So for simplicity again say 10M devices this time would 12M devices just to keep pace, but add 5% more of the total market and your looking at around 13.2M which is about a 33% increase in total number of devices sold.