What the cart counts for

By default the cart is measured exactly as WooCommerce measures it: the line subtotal, including tax if your shop displays prices that way, with coupon discounts subtracted only if your Free shipping method is set to subtract them.

You can override that under Setup → Cart Total → Coupons and discounts if you want the bar to count the cart before discounts, or after them, regardless of the shipping method's own setting. Leave it on Follow the shipping method unless you have a specific reason not to — that is the setting that keeps the bar and the checkout in agreement.

You can also leave whole shipping classes out of the total, which is useful for bulky items that never qualify for free shipping.