AWS - How my single EC2 micro instance can cross 750 hour limit?

I am new to AWS, my site is up and running since three weeks. While my billing shows:

Service      Month-to-date   actual usage   Month-end    forecasted usage   Free Tier usage limit
EC2 -Linux   750.00 Hrs      100.00%        930.00 Hrs   124.00%            750 Hrs

Also Amazon site states that:

750 hours of Amazon EC2 Linux t2.micro instance usage (1 GiB of memory and 32-bit and 64-bit platform support) – enough hours to run continuously each month*

While there can be maximum 31*24 = 744 hours in a month, so how can my single EC2 instance exceed the limit just in three weeks in terms of number of hours? Would appreciate any help to make me understand.

thank you.