1. new worksheet, fill column A B with row number, plot scatter

2. open PD, go to drop lines tab, enable vertical drop line

3. select show at specified points only, set value to 0

4. go to label tab, enable label, select show at specified points only, set value to <drop line>, ok

5. open axis dialog, set x scale to 19.5

==> label show for 19, but drop line does not show