What you could do is disable the autocapture stuff except when you're not raiding by typing


/grss noloot

This will stop the loot popups.

Alternatively, if you want it to not do epics, you could actually edit the GuildRaidSnapShot.lua file (the actual program one in Interface\Addons) and look for this chunk:

local GRSS_Colors={
--[[["ff9d9d9d"] = "grey",
["ffffffff"] = "white",
["ff00ff00"] = "green",]]--
["ff0070dd"] = "rare",
["ffa335ee"] = "epic",
["ffff8000"] = "legendary"
};

And change it to this:

local GRSS_Colors={
--[[["ff9d9d9d"] = "grey",
["ffffffff"] = "white",
["ff00ff00"] = "green",
["ff0070dd"] = "rare",]]--
["ffa335ee"] = "epic",
["ffff8000"] = "legendary"
};

Then only Epic and Legendary items will be captured.