fReachSize < fMaxReachSize: failed (TerrainMakeLighting.cpp,529) error message in mudrunner editor

I'm a new member to Focus and I'm sure there's a place for this question / problem but I haven't got time to search for it and I'm hoping there's an answer, advice or a solution to this error message I got when using Mudrunner Editor. I can sort of work out I've ran out of room. I've only just started making the map, what's it mean? What should I do? All help appreciated. Thanks.

It's ok. I'm learning to use the MR Editor and I just learnt what all the info is in the bottom screen. It's running info about what's happening and is says: info terrain: too many visual blocks, downsampling lightmap (resolution x1). Well there you go. just solved my own problem and maybe someone else's later on. All the best 🙂