The "Total" tick as indicated by the summation of world tick + TileEntities + entities is at 10.827 ms in the screen above. The tick time, however, is 38.264 ms? Where does this discrepancy arrive? Going through each bit of the server timing, nothing sticks out at me as adding the extra 28 ms of tick time. How is Tick Time calculated, exactly? Opis documentation says it is a real time snapshot of the tick over the past 20 ticks.
Windows 8.1 64-bit
i5-4670k stock
r9 280x stock
16 GB RAM
Allocated 5GB to server. This is an established server with a lot of machines running and chunks loaded, currently nobody is online. Here's what I'm looking at on the server right now, constant "can't keep up" warnings: