I've tested an elf wizard equipped with a quarterstaff in many of the OSes, and I get different numbers in many of them, usually incorrect.
The character in question: elf wizard, stats STR 7, DEX 15, CON 13, INT 18, WIS 10, CHA 9 (after race bonuses, 15-pt buy), equipped with only a quarterstaff.
The 'standard' sheet lists the attack modifier as -10/-10; I believe it should be -6/-10. The separate "head" weapon blocks list -6 for primary and -10 for secondary. The statblock sheets (the couple I tried) list just a -2 attack modifier. The PDF sheet acts like the standard preview. The Fantasy Character Sheet doesn't list a double-weapon, but it lists it head-by-head, and lists -6 and -10.