Your addition should have added 33ppm fc in that pool volume.
Something is off.
Either your chlorine was stronger or your pool volume is less

Definitely get that figured out & be sure to do all the things ….
For a successful SLAM Process
you need to continue to MAINTAIN Slam level fc for your cya as often as possible (multiple times per day is best) until you meet ALL 3 end of slam criteria-
You are done when:

CC is 0.5 or lower;

You pass an
Overnight Chlorine Loss Test
AND

The water is clear.
(Crystal Clear w/no algae dead or alive)
Do ALL the things

*Check & scrub every nook & cranny where algae may hide {light niches, steps (inside & out), drain covers, ladder handrails, skimmer throats/weirs, abandoned lines, autofill, overflow drains, seam flaps, etc.}
*If water can go there, algae can thrive there.
*Run slam level water through all water features & lines for at least a couple hours a day during the
SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.
Slam ON
