This condition checks if the back payout and lay liability of a given selection are more or less equal. This is needed to make sure that all the greening-up / loss distribution is done for this selection, and a new cycle can be started.
So yes, if the difference is 2.0, this condition will fail and the block will not be closed.
Not sure about the other question, I guess it is too specific and related to a particular trigger I'm not aware of.