I am trying to replace my white-rodgers 1f58-72 thermostat with a hunter 44860 programmable thermostat. My system is a Rheem RPLA-025jaz I have a couple of questions:

Where do I connect the brown wire that was connected to X1 on the white rodgers? (Does anyone know what X1 coincides with?)
My system does not have an E wire so do I put the jumper from E to w2 and the w2 wire in the same terminal?

Here is the terminal sequence for the hunter: Here's the wires I have for the White rodgers:
Y1 L Y1
W2 O W2
G E G
RH W1 RH?/RC/R? (ONLY HAS A RED WIRE LABELED R)
RC/R B L
X1
B
I have already labeled my wires and can hook those to the new thermostat, but can someone please confirm that I am correct in matching up the letters and from the old and new thermostats. And can someone please tell me what the X1 wire is?

Thanks,

Nikki Clayton