Stationary bike allow override Connect distance, speed, cadence field

I just finished my first Garmin IQ app reading out the distance, speed and cadence from my Domyos Fold hometrainer.

https://www.decathlon.nl/p/hometrainer-eb-fold-opvouwbaar-en-connected/_/R-p-326799

It uses the Bluetooth FTMS protocol to provide the data unfortunately it seems that Garmin doesn't implement this, thus I can't pair to my hometrainer using the the traditional way.

So I've decided to reverse engineer the protocol and implement the protocol as an Garmin Datafield but to my disappointment the Garmin IQ API only allows you to log extra datafields but not to override the existing fields.

As a result my sessions are logged with 0km distance, no cadence and speed and I can only plot the extra fields.

Activity IQ Fields

Activity Overview showing no distance and no average speed

The Garmin Toybox API mentions nativeNum but that doesn't seem to work and I'm a bit clueless on which number to take

https://developer.garmin.com/connect-iq/api-docs/Toybox/ActivityRecording/Session.html#createField-instance_function