Symptoms
When using a smartforms expression or custom style to display milliseconds using the documentation (https://help.k2.com/onlinehelp/k2blackpearl/userguide/4.6.5/webframe.html#date_and_time.html), the outcome is displayed (for example) 12:37:44:ffff.
Diagnoses
The documentation was found to be incorrect.
Resolution
In order to get this to work in Smartforms, you need to use FFFF as opposed to ffff. A documentation enhancement request has been logged to correct this.