2x standard weetabix are a hex B on the extra easy plan. Not all the literature shows this but the website list of healthy extras does have it so you are safe to use a Hex B on them. Indeed, my consultant recommends 2 weetabix as a breakfast choice simply because it is more substantial than 28g of the other listed cereals. I haven't used a cereal hex B for ages but I used to have the shredded wheat bitesize and 28g of that is about 13 pieces, which is what, 3/4 mouthfuls?
Don't worry about it, your choice is fine and on plan.