What is the "watermark" field in TFS?

Question

At my currrent workplace, we're using Team Foundation Server (TFS) (2015 I believe), at my current workplace, and I noticed the "Watermark" field -- what does it mean/represent?

Answer 1

This filed value is a mandatory number increased by system.

Any work item field's value change will cause the System.Watermark field value change.

You don't have to pay much attention to this field.