On all the modules I've seen, R2 is 22M (or at least it's supposed to be !). Red, red, blue, silver equals 22M with 10% tolerance.
In fact I don't think it really matters, so long as its high! When measured, they're usually all over the shop.
On a similar matter, does anyone know if there's some method of determining the value of surface mount components ? There's usually nothing written on them. I supsect you're just supposed to "know" what their values are.
Rgds.