The Quantity chart is used to track numeric quantities recorded inside your forms. Common examples include tracking labour hours, number of people, costs or production quantities.
For these numbers to be tracked using a quantity chart, they must be recorded inside a table, using either a number or formula column in a default table. (or if using a prefilled table, only number or formula cells).
If none of your templates contain a table containing a number or formula cell/column, the Quantity chart option will be disabled.
For more information about setting up analytics charts (including Quantity charts), see this article: Click here