Keisha’s short version is right. The detail, as I explain it to new starters:
The chip rate equals the bandwidth, so at 125 kHz you get 125,000 chips per second. One symbol is 2^SF chips, so a symbol lasts 2^SF / BW: about 1 ms at SF7 and 33 ms at SF12. Each symbol carries SF bits. With the 4/5 coding rate that gives a bit rate of SF × BW / 2^SF × 4/5, about 5.5 kbit/s at SF7 and 290 bit/s at SF12. Each SF step roughly halves the bit rate and doubles the airtime.
In EU868, assuming that’s what your gateways run, the DR numbers are just names for SF and bandwidth pairs:
DR0 SF12 125k DR3 SF9 125k
DR1 SF11 125k DR4 SF8 125k
DR2 SF10 125k DR5 SF7 125k
DR6 SF7 250k DR7 FSK 50 kbit/sSo the vendor’s SF9 is DR3. You don’t have to set anything for that. ADR (on by default) moves each device within the profile’s Lowest/Highest DR range, DR0 to DR5 by default, based on the best SNR over its last 20 uplinks. A meter that hears the gateway well ends up faster than SF9, a far one stays slower. After a change you can see it in the device’s lora.dr attribute. The one case where you’d turn ADR off is anything that moves, like a tracker.