The Threshold Cnt is the number of records written to the queue before the task is invoked. When the threshold is reached, the specified task code will be invoked. Depending on what the task does, the count will go down (typically the invoked task reads the queue and deletes the queue records as they are processed).
The 'Max Rec Cnt' is the maximum record count (that is, the maximum number of entries permitted in the queue; if 0, no limit exists) When the number of entries in a queue reaches a specified upper limit, the DC/UCF will not permit further entries to be directed to the queue. The transaction will usually receive a 4407 error.