Tour de Fleece Part 3 - Recalculating

For the Guild challenge, we were supposed to receive 150 grams of fiber. I didn't remember to weigh the whole mass at the start before I began spinning it, but I weighed 75 grams of the remainder and assumed that would make my halfway point. So here's my current progress. Bobbin 1, supposedly the half of my quantity.

Bobbin 2, after yesterday's spinning.

And the fiber I have left to spin.

Do you see where I'm questioning my calculations?
It looks at this point as if the 75 grams I weighed out was not half the quantity, but closer to 2/3. Which in turn suggests one of two things. Either my scale is off significantly, or my initial quantity was less than I thought. We shall see which it is when everything is spun and plied, and I weigh it again. Right now, I have simply split the remaining roving into 2 slightly unequal parts, to be divided between the two bobbins.
On the positive side, each bobbin will be fuller than I thought, so more total yardage, and a better chance of getting a good-sized shawl out of it. Silver lining to every cloud, etc. Although I'm not sure the people at Bluesfest are thinking that way today, after a stage collapsed in the storm last night. Fortunately nothing lost here, apart from a few shingles and branches.