One #silverBlue annoyance is that if you are doing manual partitioning (in this case, reserving disk space in case the school unexpectedly creates a need to run Windows at some point), there's insufficient guidance on partitioning. The documentation points out that the installer doesn't know about Silverblue limitations, and so describes what partitions/file systems you can and can't create, but has nothing on expected sizes. Hopefully we guessed right. 🤞