Two thoughts....
Are you measuring in ounces or converting to grams and measuring in grams? Grams will be much more accurate in the quantities you are talking about. The 18.5oz bag makes 25 pounds per the directions. That works out to 0.74 ounces per pound. Which is 20.9786 grams (or 21 grams per pound of meat). And that leads to my follow up question....
What scale are you using to measure the #116?
Larger capacity scales are not as accurate with smaller amounts. Also scales need to be check for accuracy every so often with a known calibration weight. They also will start to read weird when the batteries are getting low. I have a smaller scale that reads down to 1/100th of a gram and it has a 500g max capacity. That's the one I use for all my spice and cure measuring. I also have the 100g calibration weight and double check the accuracy both before and after weighing out all my spices. I found it was over 100g off just before the batteries flaked out on me (but that was obvious). That's why I double check both before and after and then move the spices/cure to a single container for mixing once weight is verified.
For example I have a Ultra-Ship scale that weighs up to 55 pounds and the smaller one that has 1/100th a gram resolution. Trying to measure out 1.13 grams of cure#1 for a single pound of meat on the 55 lb scale is an exercise in futility. It's a dream on the smaller and more precise scale. The big scale advertises 0.1 ounce accuracy for weights under 2 pounds, but that is 2.834 grams!!!! So my 1 gram of cure can actually be nearly 3 grams and still be within specs for that scale (and way too much cure). And if that 0.1 ounce accuracy is a +/- rating then you can double that range to a 6 gram bracket and still be considered in specs.
Depending on what scale you have, the calibration weight may be different, but most of the digital ones can be re-calibrated. A United States nickel (5 cent piece) weighs exactly 5 grams, so in a pinch that would be a good alternative to test the accuracy of a scale. Here is a list of the official weights of US coins from the US Mint.
Cent (since 1983) - 2.500 g
Nickel (since 1866) - 5.000 g
Dime (since 1965) - 2.268 g
Quarter (since 1965) - 5.670 g
Half Dollar (since 1971) - 11.340 g
Golden Tone Dollar Coin (since 2000) - 8.1 g
Here are my 2 scales. The smaller one was around $19 on
Amazon and the larger was around $28 when I bought them. I think the 100g calibration weight was like $7.
