One aquastat is a 6006, it is set at 100° . If the temp goes below 100°, it kills the power to the EFM and will energize the oil boiler. The other aquastat is a 4006 and is set at 240° for a dump zone. With just a couple days of operation, I'm not even sure I need one as I haven't seen the temperature rise more than 5° on idle.
I really like the Hydrostat. This was my first install using one. I'm quite impressed, and the remote mounting is a bonus. Made the wiring much neater. The price is right and so is the quality, I'll be stocking these for replacements.