Pension asset ceiling

When your pension is overfunded, the amount of asset that can be reported is the lower of the surplus and the asset ceiling. This consists of the present value of future economic benefits, such as refunds from the plan or reductions of future contributions.

Can someone give me an example of what refunds and reductions of future contributions would be?

What is the reasoning behind putting a ceiling?

If the plan is overfunded, the sponsor has the (unilateral) right to withdraw the excess or reduce their future contributions.

The ceiling takes this right into account.