Strange screen resolutions

My reports results in variety of strange screen resolutions. 911x512, 1846x1154, 1366x768, 1344x840, 1438x808 and so on.
What is being measured? I use Piwik 2.15.0.
Could it perhaps be a result of iframes used on the pages i track?


please upgrade to latest Piwik and if you still have the issue with new visitors, create a bug report @ Issues · matomo-org/piwik · GitHub