Here is a reference guide for ditafm-output.ini
https://help.adobe.com/en_US/framemaker/2017/ini/framemaker_2017_ini_reference.pdf
This ini file has lot of settings that you can use in terms of how you would like to output your PDF. I am assuming you have multiple topics and finally you want to generate a composite file (single file) and then generate PDF. Another option is to generate the PDF for your ditamap like a Book with multiple chapters.
For the former one, we have the following template in sts file ditabase1.3.template.fm

Simply export it and then make changes onto it for configuring how your PDF looks like
Ex: if you export and then finally open in FM the same file and go to Master pages you can change the Chapter 1 to not show.
Regarding numbering, since this number is for the main title title.0 simply change the numbering as in Paragraph designer

Currently it is set to C:<$chapnum> since chapter number is 1 so it is consistently coming 1 , instead you could remove it or have your own using some of the building blocks.
All the above is UI driven so just use the UI for making these changes in template and finally generate the PDF.
Some links which may be helpful
FRAMEMAKER 11: Easy PDF output from DITAMap - YouTube
Customize the look-and-feel of FrameMaker 10 DITA 1.2 templates – Adobe TechComm Blog
only change with FM2019 is that instead of output template being earlier in installation directory, that has been moved to sts file.
Hope this helps.
Thanks
Amitoj Singh