Help users understand requirements and constraints. Be specific. Don't assume that users know the limitations of your system.
Not recommended
The combined size of the attachments is too big.
Recommended
The combined size of the attachments (14MB) exceeds the allowed limit (10MB). [Details about possible solution.]
Not recommended
Permission denied.
Recommended
Permission denied. Only users in <group name> have access. [Details about adding users to the group.]
Not recommended
Time-out period exceeded.
Recommended
Time-out period (30s) exceeded. [Details about possible solution.]
Next unit: Explain how to fix the problem