[Therion] export bbox

I'm not sure I understand the new bounding box feature. Therion Book 5.3 pp55 to57 I expect I could use syntax like , export bbox -output ../Outputs/MiddleEarth-bbox.txt however it gives an error like D:\Program Files\Therion\therion.exe: error -- thconfig-MiddleEarth.thc [84] -- unsupported export type -- bbox The summary on p57 suggests this might work, export special -output ../Outputs/MiddleEarth-bbox.bbox but the same type of error is encountered. Bruce