Here's what the manual says:
---
FIRING THE SW99 QA
The SW99 QA features a quick action (short double action only)
firing mode.
Pull the trigger through the full length of travel to fire the pistol.
After loading or firing, the trigger will be in the forward position
and the cocking indicator will be visible.
FIRING THE SW990
The SW990 features a double action only firing mode wherein
the first trigger pull and all subsequent trigger pulls will require
the same amount of travel and force.
Firing Double Action
Pull the trigger through the full length of travel to cock the
striker and fire the pistol. After loading or firing, the trigger
will be in the forward position and the striker decocked
(cocking indicator will not be visible).
FIRING THE SW990L
The SW990L features a short double action only firing mode.
Pull the trigger through the full length of travel to fire the pistol.
After loading or firing, the trigger will be in the forward position
and the cocking indicator will be visible.
---
To be honest, it sounds like a QA trigger pull without a decocker or pre-cocked striker... rather confusing actually. I haven't fired either one; so hope the text above helps.
thorn