Mine was, as I recall, 0.1 oz. over the weight given in the GG website specifications. I bought it about a year ago. This was before seam sealing but included the stuffsack and the chunk of guyline they sent with it, which was at least 5 feet more than was needed. Obviously, seam sealing will add to the weight. I have since sold the Spinntwinn so can't verify. I discovered that my dog is restless all night under a tarp, so I'm back to the tent.
My experience with Gossamer Gear is that you can trust their website specifications. Of course if you're dealing with an older model bought used, the website specs could have changed. However, their outstanding customer service folks can undoubtedly dredge up older specs if that's the case.