Need help with a safe level of Ash & Magnesium in both canned & dry cat foods.

I'd like someone to help me understand a bit more about the safe levels of Ash & Magnesium in cat foods.
My Kally Kat now wants to eat only canned chunky, meaty meals. She won't eat the pate' stuff anymore. I'm feeding her top quality Grain - Free canned foods about 2 1/2 TB in am & 2 1/2 TB in pm. She's also eating Serengeti's Grain - Free Dry about 3 to 3 1/2 TB thru-out the day & last meal at night which is her 1 TB dry. My concern for her is, is eating canned foods better than dry foods? I read at Wellness Pet Foods a top quality pet food Co, says that a safe level should be under 2. 5%. low enough not to pose any risk of Urinary crystal formation.
I went to Drs. Foster & Smith Pet Education site & the Nutrition in Forum, but would like to hear from other Catster members of their input or knowledge about Ash & Magnesuim in our pet foods. BTW Kally is 10 lbs. moderately active & very happy.
Thank you,
Purrs from Kally Kat's Mom Liz (:

Asked by ♥Kally Kat♥DG#33 on Dec 4th 2008 Tagged foodnutrition in Food & Nutrition