Speedtest results seem strange

Just got this R7000 and hooked it up a few days ago. My old router was the workhorse Linksys 54G.... had many years and just noticed this year some slow times when video, web, phone all converged. It was never really slow.

I do notice faster speeds with the R7000. I set it up stock, and won't be flashing it till I see that I want to keep it.
One thing I noticed, whether on Lan cable or wireless, is that speedtest always starts out slow... like .5 mbps... then gradually creeps up to 30 or 40 mbps. This is with comcast.
Is there something I haven't got set right? I have used speetest for years and have never seen this 'slow start'.

Thanks