What is the unit of the set

What is the unit of the set, Total:1 items.

In the international standard classification, What is the unit of the set involves: .

SCC, What is the unit of the set

• AWWA WQTC55033 Can a Utility Afford to Operate Without On-Line TOC Analyzers Considering the Requirements of the D/DBP Rule? On-Line vs. Grab Samples: What Are the Advantages and Disadvantages?

Others:   What is the unit of the set, What does table set mean, sets of units.