The sum of the digits of the minuend is 8, and the sum of the digits of the subtrahend is 10. When using vertical subtraction, there are two borrows. So what is the sum of the digits of the difference between the two numbers?
被减数各位数字之和是8，减数各位数字之和是10．用竖式相减时，有两次借位．那么两数之差的各位数字之和是多少？
<gadget id="calculator">9 - 10</gadget>
<output>-1</output>

<gadget id="calculator">8 + 9 + (-1)</gadget>
<output>16</output>

<result>16</result>