I know that "an" should be used when a word is followed by a noun that starts with a vowel.
But what about a numerical value that isn't formally written out and used as an adjective? Such as "a 8x8 grid" is it that, or "an 8x8 grid" ?
I've received some disagreements on this in the past, so I'd just like some clearing up. Any reference to formal rules would be much appreciated.