So I envisaged that I answered 2 questions wrongly.
I was denied a US visa once but instead of mentioning it under "refused permanent or temporarily visa...."I answered NO to that question and YES to "refused admission or ordered to leave Canada or any country", I would imagine that they will know it was an oversight as I clearly stated that I was refused a US F-1 student visa to study at xyZ university on June 11th 2018.
I have raised a CSE and sent an email to Accra VO to explain myself....I hope that would be enough...
Other suggestions please ????