The best way to determine from where exactly these amounts originated is to log into your CRA My Account and look for 2018 slips using the "T4s and more" option.
On the main page of your CRA My Account, there's a section on the right for Related Services. The first option is Tax Information Slips (T4 and more). Select that option. On the following screen, select 2018 as the tax year. You'll see any/all slips on file with CRA in the Information Slip list.
