I was a student before and have a tuition certificate. would I include it under student? I tried doing that and my tax refund reduced to about 1000. why is that?

Hello, while doing my tax return, my tax refund so far was about 2477. I was a student between 2017-2018 and I have been employed since September 2018. 

I have a tuition certificate to include,  i tried doing that and my tax refund reduced to about 1000. why is that? am I reporting it in the right place, that is under student?