Credit to buy vs Credit limit

Hi there Truworths Team I am writing this review to appreciate you all. Since I opened my account I have never encountered any problems and even when I go to the store I always get the best customer service. Also out of curiosity I would like to know about your credit - When I opened an account you gave me R1000 credit limit which I didn't have a problem with. I always make sure I make my payments on time except during lockdowns where I was really struggling maintain my payment behavior due to a lot that was going on. So what I have noticed is that my account limit is still at R1000 but the amount I can buy with is R1400 and I also have R322 as my balance which I have to pay. This means after I have settled my account the amount available to use will become around R1,775. How does this work because I am sure it is not an increase for credit. Just want to understand how it works because I don't think I qualify for an increase at this point since my credit score is not where I think it should be. I would love an increase in the future and I am sure that will be offered to me without me having to ask for it, correct? Anyway my only question is directed on how does one get to have more credit to buy compared to credit limit granted?

Thank You for being an amazing service provider.

Sincerely K. Mkhize