You don't need to factor them into your water/grist ratio, but the will absorb water eventually, so you'll need to increase your sparge water. It's probably a small amount of water though and wouldn't matter if it was added to the mash or sparge. In any of these situations (including steeping) just make sure that the total volume of water added (during mash, sparge, and steeping) is the same and you'll end up with the volume of beer you want. ie - Yes, 1 gallon of steeping water should be removed from elsewhere in the process, probably the sparge.