Could his label read "BL" maybe for Bullseye, a very popular pistol powder. If so that would be a mild load. And as Bullseye is one of the faster powders.....4.0grs of just about any powder available would be a mild load.
But reloads by others run the whole spectrum....the very best ammo in the world to the VERY WORST!
My loads in this caliber using Unique and W-231 are at 5.0 gr. or less and they are on the light side. Target loads can tend to be on the light side anyways. Faster is not always better or more accurate. I'd say this ammo came with good provenance so you should be OK using them if you so choose. I am leery of someone elses reloads unless I know them and know their practices.