Two responses in less than three hours, so that's already going against what you predicted. tsk tsk
On a more serious note, the staff handbook serves as a guideline for potential sanction that a staff member can utilize when dealing with a situation, not mandates. Quoting the staff handbook specifically:
"We trust that our staff can deal with Sits/Issues with Fairness, Honesty and common sense. There will not be a guideline for every punishment so it will be up to you the staff member to decide if you are having an issue deciding what the punishment should be asking another staff member. "
"Not all situations require punishments. Some staff may decide to let players off, while others may feel they need to punish. This is the call of the staff member and should be done by a case by case basis."
This essentially gives staff members the discretion to issue sanctions as they deem necessary.
However, given that this was your first offense and that it was an unusual situation of a custom D-Class having restraints I would + Support lowering the ban to 24 hours.