Hi, I'm a new seller from Singapore region,
The shopify payments says "lower credit card rates - 3.1% + $0.50 (online)"
Yeah, I think so. It means with each your order with a credit card, you will be charged 3.1% value of the order plus 50 cents.
By the way, if you have any trouble with Shopify while doing business, these guides for Shopify business would be useful
Hope it helps!