i got a nice sirloin tip roast marked 3.70 lbs. several days later i sliced it in 2 for a couple different recipes. one piece was 1 lb 8.8 oz and the other was 1 lb 15.5 oz for a total of 3 lb 8.3 oz, there was also 1 soaker pad and a little loose juice that i didn't weigh because at the time i was not interested. i used a digital kitchen scale that could be off but i never have noticed, when i use it it is for baking.
do you know if that weight discrepancy is typical (3.70 lb or 3 lb 11.2 oz vs my measure of 3 lb 8.3 oz)? only 3 oz difference, when figuring in my head it seemed more.