The points dist didn't come with the '76 225. Eiter it's the original '72 dist or someone changed it on the '76 motor.

2* 30' is 2degrees 30seconds, or 2 and 1/2 degrees (2.5*)

Intial timing will depend on what year and application the dist you are using is for. The mechanical adv was different for different models and years. A dist with 7.5R adv plate and 2.5* intitial adv will only give you 17.5* total. On the other hand, a 14 R adv plate and 2.5* intial will put you close to the desired 30* total a slant six likes.
A '72 Dart will like between 8* and 12* int adv, a lighter car and/or lower rear gear will like more int adv. I'd try a 10R plate and 10* int adv to start. I run a 9R plate with 12* int in my street '68 Valiant 200, the track '68 Valiant Signet gets a 7.5* plate with 15* int.
If you don' know the mech adv, keep bumping the int up till it pings under load, then back it off 2*.