add up یعنی چی؟ با یه جمله مثال بزنید لطفا

1. برای جمع کردن اعداد:  

If you add those four figures up, it comes to over £1,500

2. افزایش: 

The changes in air quality are small, but after a while they do add up and affect people's health.

3.منطقی یا محتمل به نظر رسیدن:

 John claimed he was at home at the time of the murder, but police said his story didn't add up.