Doubt in contract costing?

1. Why is uncertified work shown in balance sheet?

2. Why is WIP reserve deducted from WIP in balance sheet?

Is there any material I can read to gain clarity on this chapter? I have looked at many youtube videos and the textbook but they do not explain the concept in enough detail. I know that I can by-heart but I want to know the meaning and reason behind the steps I am performing.

Off-topic:

Also, why are there 2 discussion forums for IPCC here? What is the difference?