missed estimates and they sold less iphones than last year, which was a down year...
EDIT: also, last year's flagship iphone sales number is also inherently lower as the iPhone 7 was released in Q3. This year, the iPhone X came out in Q4. So this year's numbers, which included ALL new iPhone sales in 2017, still didn't beat last year's lower and truncated iPhone sales number... I'm not sure that's a positive.
That should cut the other way. This year, the top-tier model (the iPhone X) was only available for a little over 8 weeks of the quarter while last year the top-tier model (the iPhone 7 (and Plus)) was available for all 14 weeks of the quarter.
Also, the iPhone 8 (and Plus) were only available for 13 weeks (in Q1) this year whereas the iPhone 7 (and Plus) were available for 14 weeks (in Q1) last year. And all of those models were available for 9 days in the previous quarters.