I don't know whether the credit limit is insufficient when you use the card or the credibility is insufficient when you apply for the card.

Insufficient credit limit when using the card: because your card credit limit is less than your consumption limit, you can make up the difference with cash.

When you apply for a card, you are told that your credit is not enough: that is usually because your credit history is tainted, or your income is not enough to bear the risk of credit limit.