OK I looked at again and I had missed some important things, the "Bag Shot" is only shown in 10-inch caliber. The reference was right over a separate line for "grape shot" with same wording, so that means to me it is different from grape shot, if that helps any. I'm thinking at that post the only 10-inch weapon they had was one or more brass howitzers, so maybe the bag shot was for the 10-in. howitzer only.
"Hard to read"
It is hard to read as it is posted, but you can go to "zoom" which is under "page" on my browser anyway, on upper right of page near "tools." Zoom in to at least 150% and it should be very legible. Or you can use a magnifier.