This factor is essentially based on your credit utilization, which is your credit card's balance divided by its credit limit.
The lower your credit utilization ratio on each card and across all your cards, the better. So, in this case, having multiple credit cards can actually help your score by increasing your overall credit limit and spreading out your balances across multiple cards.
For example, let's say you have one credit card with a $3,000 balance and a $5,000 credit limit. Your utilization rate on the card is 60%, which would negatively impact your credit score.
If, however, you have three cards with a $1,000 balance and a $5,000 limit on each, your utilization drops to 20%, which is generally much better for your credit.