It's an icon of the last hour reduced to a clock with a 1 on it. The 1 is centered in the middle of the clock. The clock also has a counterclockwise arrow running all the way to 11 in order to symbolize there is 1 hour left.
This is a Countdown icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,100 icons, all in the same style and quality.