RTP asset discovery technology is discovering clicks on links that direct to files such as: PDF, YouTube, PPT etc.
Also, it uses predefined URL patterns to count an HTML page as an asset (see: Enabling Asset Discovery - Marketo Docs - Marketo User Manual).
When this is the case, it is required to code the asset discovery events in the page.
The way to do it is by using the rtp( 'send' , 'view') API call.
NOTE: this method can be used only with RTP API tag version
This is how the code should look like: