cc2520: issue of CC2520 TXPOWER register

Hi 

We have a CC2520 +CC2592 radio system in production. Now have a issue with TXPOWER regigister setting when review and try to improve the program.

the datasheet at page 72, give a table, and in SmartRF studio7 v2.8.0 when ENABLE "Range Extender: cc2591", and TX_power=17dBm / 19dBm, software gives the value 0xF9/0xFF for TXPOWER register, both NOT listed in the table, Datasheet gives the similar value is 0xF7 /0xF2.. So which value i can trust? 

And both 17dBm / 19dBm TX power tested with frequency analyser is good. but 17dBm cann't link to 19dBm module stable. 17dBm, with register 0xF9 can link each other very well.