While there isn't a single "guide" with that exact file size, the number typically appears in the context of specific software updates and data files. Based on recent records, here are the most likely "topics" you might be looking for:
: For hardware developers using the Intel Quartus Prime design software (v18.1), the device support package for the Cyclone 10 LP family is exactly 266.1 MB . (266.1 MB)
: On the Apple App Store, the puzzle game Hole Match Master - Gather game by Shinrays Games is listed with a download size of 266.1 MB . While there isn't a single "guide" with that
Fixes for unresponsive or incorrectly displayed . Resolution for "Find My" requests made through Siri. Fixes for unresponsive or incorrectly displayed
Security patches for the Safari browser engine (WebKit) and the Kernel.
If you were looking for a literal PDF or document guide of this size, it might be a local file or a less common manual. Are you trying to or find a specific manual for one of these? iOS 16.3.1 Review! (Features, Changes, Etc.)