You may be looking at the garbage PDF...especially if you filed Federal first, and then came back later and filed the IL forms.
The early IL-1040 forms used the 2016 tax rate.....and couldn't be filed because they hadn't been updated to the higher 2017 tax rate. a lower refund would be consistent with the proper IL-1040 2017 tax rates.
Print/save the proper PDF as follows.
https://ttlc.intuit.com/replies/6734971