10% of 14 inches is 1.4 inches or 1 and 1/3 inches. Your amels are between 12 and 12 1/2 inches long (give or take a few 16th's).
If you have a scale with a TARE function first put the tub/bag on the scale, hit TARE, this will zero the scale reading. Then when you return the tub/bag with the snake in it you will get only the weight of the snake, even tho you weighed the tub/bag as well. If you do not have the TARE feature you weigh the tub/bag with and without the snake in it, then subtract the weight of the tub/bag alone from the weight of the snake in it, there is the weight of your snake.
The easiest way to measure the length of a snake is to put them in some type of clear container, or a glass tank that is long enough for the snake to stretch full length of. They will eventually cruise along the edge and allow you to either measure directly along the snake or mark it to be measured later (when you find the damn ruler [don't ask]). I said this is the easiest remember, not necessarily the fastest method as I am positive the snakes like to mess with our minds and won't co-operate when we want.