It would probably be best if we could see all of your test results as of today to get the full picture. But previously at a CYA of 40, your SLAM FC level would've been 16. Your sig implies you have a multiport valve and the ability to backwash, so it's very possible that you've depleted some CYA during those backwashes. The minimum CYA for a SLAM is 30 to provide some top-cover from the sun. If that CYA dropped low as you suspect, your FC hasn't been protected enough therefore the SLAM may not have been as productive.
So now that you've added more stabilizer, once it dissolves it should increase your CYA in 24-48 hours. If your new CYA target was 40 again, plan on maintaining an FC of 16. If you find that your CYA went a little higher, closer to 50, then your SLAM FC level would be 20. In addition, if it's been a long time since you've checked pH, I would do that before raising the FC again. Make sure to test pH when the FC is below 10, then increase FC back-up to the appropriate SLAM level based on your new CYA. As with all SLAMs, make sure to review the SLAM page to ensure you're not missing something you should be doing each day (i.e. scrubbing, inspecting ladders, behind lights, etc.).