Now you are in the right spot. I'll be interested to hear what's going on in Shelby myself. Based strictly on the lease terms you mention, IMO the royalty is too low for the acreage you own and the length of the primary lease term plus extension option. The bonus is the least important term but with 275 acres it's worth negotiating also. I'm sure other Shelby members would be interested in what company is making the offer. They might have an opinion on whether this offer comes from an operator (a company that actually drills wells) or from an investor hoping to assign the lease to an operator and make a profit.
It may take 24 hours or more for all the members to see the email notice and to make replies. It's always best not to get in too much of a rush even though landmen often push for a quick decision.
That area is generally considered to be a poor rock quality for a shale well, but maybe they are looking for something conventional.
Yes - Don't have land, but own some minerals in the general area. It depends on which survey your land is in. There's a little bit of activity now - do you have a description of the land? - GR