Create Order for $100 but capture $1000 without the customer knowing?

[riscarrott]

I'm integrating with PayPal Checkout (I think previously called Express Checkout?)

In the sandbox environment I've found I'm able to create an order for an amount, e.g. $100 and upon approval I can update the order amount to say $1100 and I'm still able to capture this higher price -- is this only allowed in the Sandbox environment, what would happen in production as it doesn't seem right?

e.g.

window.paypal
      .Buttons({
        createOrder() {
          // Create order with amount === $100
        },
        onApprove() {
          // Update order amount === $1100;
          // Capture $1100 even though the customer thought they were being charged $100?!
        } 
      })