You never stated what kind of gear it is.
If it is a purely fabric garment, then it ought to be closer to the spec. Note that some manufacturers will call the weight for a medium size, and if you purchase a large size, then it will weigh more.
If it is a down item like a sleeping bag, then humidity may make the weight inaccurate. When they manufactured it, the down was extremely dry, so you get one standard weight. Then, if you leave it out in the humidity for a while, the down absorbs water (weight). If you think that this might be the case, then place it in a clothes dryer and run it on very low heat. If it does weigh less afterward, then humidity was at play. Note that if you use too high of a heat, then you can damage the item. All you want is 10 or 20 degrees F warmer than ambient.
Also, it is not clear what was custom about this. If it was a custom size, then that would account for weight change.