Capped Ranger Double strike/Offhand math?

[f_gamer]

Hi. I am a little confused on how Double strike and Offhand are calculated. Fully equipped with Heavy Maces, I see 26% DS and 50% OS. Using light weapons, I see 15/35.

Here are the bonuses I am aware of: TWF->GTWF+PTWF+WhirlingSteel+Whirlwind+Dervish+Improve d Scourge weapons(5% DS)-gives oversized two weapon feat+Greater Scourge weapons (5% DS and OS)+1% Filigree bonus+10% artifact bonus to DS/OS

Does the 26%/50% make sense? I would think main hand would be much higher. My base DEX is 14 with a +2 tome but Ranger auto-granted GTWF. Thanks