Given this reference test, what is the daily recommended amount of magnesium for women in the U.S.?

In the UK, the recommended daily values for magnesium are 300 mg for men and 270 mg for women.[67] In the U.S. the Recommended Dietary Allowances (RDAs) are 400 mg for men ages 19–30 and 420 mg for older; for women 310 mg for ages 19–30 and 320 mg for older.

The daily recommended amount of magnesium for women in the U.S. is 310 mg for ages 19-30 and 320 mg for older.