Set ringer amount on Panasonic KX-TG7230E cordless phone with answer machine?

I have a Panasonic KX-TG7230E cordless buzz with answering machine system with my ancient Panasonic buzz, I was able to set the ringer amount (2 rings, 3 rings, 7 rings .etc) but with my current Panasonic, the default is 4 and I can’t see any way of varying it.

So is there any way of varying the ringer amount to 7 or will I have to take it back?

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