Hot water wiring and thermostats

I cleaned the lime out of my electric water heater and installed new elements and thermostats. I followed the wiring diagram when hooking up wiring. I turned the breaker back on and checked voltage. It showed 240 volts across the element, but was not heating. I also pressed the reset button on the thermostat. No heat up. After waiting a while, I decided to put the lead on number four on the thermostat to the number 1 on the thermostat. Both elements kicked and started heating. I know that most dual elements heat independently of each other. What problem might I encounter by the wiring that I did ??