I would actually recommend the Light Ash Brown: Suitable for base shades 5 to 7.
Its a good idea to choose a shade darker than you might think suitable because you can always dilute the results by adding a normal conditioner.
So I would recommend doing a strand test using the light ash brown and if you felt it too dark, then you can mix a 50/50 light ash brown with a normal conditioner and then test those results.
Choosing a slighter darker conditioner means you have many more options and the bottle will last much longer.
It recommended that you apply the conditioner to slightly damp hair.
But I've found that if you apply it to clean dry hair, the results are stronger.

I offer forum members a 5% discount if they order directly through me (as opposed to ebay) and anyone can do that by emailing me at [email protected]

My hair is #22r and I use the Dark Ash Blonde as I find the hair a bit too yellow and my natural hair is a paler grey blonde version of yours.