Counting the number of instances an item from a drop down is selected is possible using the COUNTIF() formula.

To start, navigate to the left tab and choose either a 'Prefilled' or 'Default' under 'Table. The formula is possible for the two. You can set your table and choose whichever column is intended for the drop down selection.

For a prefilled table:

You can add at the last row a cell as your display cell. Use the formula,

For example:

Cells A1 to A5 contain the drop down list, and you're counting for the number of instances "Project Manager" is used. Use the formula,

For a default table:

You need to add a prefilled table to set your display cell and cross reference the formula to the previous table. Use the formula,

For example:

Table 1 Column A contains the drop down lists and you're counting for the number of instances "Engineer" is used. Use the formula