Limits in Custom Settings:
1. The total amount of cached data allowed for your organization is the lesser of these two values:
i. 10 MB
ii. 1 MB multiplied by the number of full-featured user licenses in your organization
2. Each Certified managed package gets its own separate limit in addition to your organization limit.
3. 300 fields per custom setting.
4. You can’t share a custom setting object or record.
5. No owner is assigned when a custom setting is created, so the owner can’t be changed.
6. Custom settings are a type of custom object. Each custom setting counts against the total number of custom objects available for your organization.