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Your score will change daily, and can change hourly.
It depends on who updates what when.
If your score bounced back to 504, then it's probably safe to believe that is your true score. As you rebuild your credit, you should see the score stay pretty consistent as it climbs up. No more wild bounces.
where did you check your scores at?
Don't compare FICO scores with FAKO scores ~ there is no correlation between them. Your FICO score is what lenders will use the vast majority of the time.
Which service are you using on myFICO? ScoreWatch?
The scores from CreditKarma are not FICO scores. I'd ignore them.