What is meant by the term "Plan Assets" in the following circumstance?

“Plan assets are reduced by undeducted contributions?”
See Gray Book Question and Answer 1990-1999, p 6. 2000 Enrolled Actuaries Meeting, Session 806
http://www.ccactuaries.com/library/onsites...000ea/806-B.PDF
Question 1993-14
Special Unfunded Current Liability Funding Limit–Various Issues

The following questions relate to the special maximum deductible limit under §404(a)(1)(D) which is equal to the unfunded current liability:
(a) Are plan assets reduced by the credit balance in the funding standard account?
Answer
(a) No. Plan assets are only reduced by undeducted contributions.

My quistion is how, and what is the significance?

Thanks for any light that can be shed.