TDS under GST

Mukul (Service) (54 Points)

12 April 2019  
referring section-51 of cgst act, 2018, specified person are required to deduct TDS in case taxable value (excluding GST and Cess) of a "single contract" > 2.50 Lakh.

In above, what does SINGLE CONTRACT mean?

Does it meant value to total taxable supply during a year or value of supply Per Invoice or Per Purchase Order.?

request clarification.. thanks