User Configuration > Administrative Templates > Microsoft Project 2016 > Project Options > Save > Tools | Local Project Cache
User
HKCU\software\policies\microsoft\office\16.0\ms project\settings
Sets the size limit in MB of the local project cache. This is applied per user profile. If this setting is enabled, the size of the cache will be set to the number specified. If this setting is disabled or not configured, users are able to set the cache size limit.