Quote from Phanx
This is intentional. Grid cannot read your mind and magically know that you only want to see certain groups. Once you enter an instance, Grid knows how many people fit into the instance, and adjusts the layout size accordingly. If you only ever want to see the first 5 groups, you could set your "40-player Raid" layout to a 25-man layout.
Layout > 40-player Raid > By Group 25
GridStatusRaidDebuff is a third-party plugin. It's not written and maintained by any of the same people who wrote or maintain Grid. For help with it, you should post in its thread:
I had tried this option, changing to 5 groups and the minute it put the 8 groups. I deleted the files grid wtf folder and checking the box last night to block cells in design I had in 5 groups. I also worked as the Grisstatusraiddebuffs.
Thanks for everything