This is worldwide is it?
Nope, just the USA and Canada, where iOS devices dominate.
What does this actually mean? More so, what significance does this have?
The significance is unknown, since we don't know a lot of other variables.
For example, we don't know if one group uses apps or widgets or the web more often. Or if one group is more likely to visit sites with Chikita network ads.
We don't even know if it's caused by certain browsers constantly reloading web pages and artificially multiplying the number of ad impressions.
Like most reports of this type, it's not meant to mean anything expect "buy ads on our network". It's just a marketing ploy.
However, since North America trends toward iOS devices, it could just reflect what we already know: there's a lot of iOS users in North America. Especially iPad users.