For those using Garmin IFR navigators and transponders, the Position Integrity setting in the transponder configuration should indeed be set to 1E-7 to result in SIL=3, and the software should be at least to the versions identified below:
(e.g. GPS 400W, GNS 430W, GNS 530W)
Main software version 5.03 or later and GPS software version 5.0 or later
(e.g. GTN 650 and GTN 750)
Main software version 3.00 or later and GPS software version 5.0 or later
Main software version 2.4 and GPS software version 5.1
Aviation Service Document
GTX 23ES and GTX330ES Transponders
Main software version 7.04 or later (V8.04 released in 2019)
The RS-232 serial output port on the GNS or GTN unit providing position data to the transponder should be set to "ADS-B+" or "ADS-B+ Format 1" when available.
The RS-232 serial input port on a GTX330ES transponder configured to receive ADS-B+ position data from a GNS/GTN unit should be set to "REMOTE".
Just a quick reminder that those of us without an IFR navigator and using the G3X VFR WAAS GPS receivers only (built into the GDU 37X and GDU 46X displays) to provide data to our 1090ES transponders will have the Position Integrity set to "VFR GPS" on the GTX23ES configuration page or 1E-3 on the GTX330ES configuration page to reflect the non-certified nature of our position source.
Let us know if you have questions.