Draw calls: how long it took the CPU to issue rendering calls, not including the time for the GPU to complete them. In some cases, rendering calls can be quite CPU intensive, especially when very large numbers of objects are on-screen. Some browsers also forward all draw calls to another thread to be processed in parallel, in which case the Draw calls measurement will likely be an underestimate.
Engine: the remaining time spent in the Construct 2 engine, which is the overall estimated CPU with the events, physics and draw calls times subtracted away. This includes processing behaviors and other engine housekeeping.