foot within 24"plate

[DaveASA/FED]

Was looking for opinions on interp for "both feet must be on the ground within the 24-inch length of the pitcher's plate." ASA 6.1.A Do you interperate this as both feet have to be completely within the 24" or just partially within? Question came up when a pitcher had 1/2 of her foot on the rubber and the other half beside the rubber. My plate ump thought this was illegal and I didn't. I had always been told as long as part of the foot was within it was OK. Who was right? Also wondering if FED is different.