It depends on your required amount that could be negotiated in each particular case. Special orders could last longer to deliver, if compared to ones of standard dimensions.

A+ Class boards are without branches.
A Class boards are with an unlimited amount of healthy, solidly accreted branches.
B Class boards could be with black ingrown and small dropping side branches.
In general, plane boards are classed by A/B
C Class boards could be with dropping side branches; planed not so flatly, also cracked, etc.