Adam found the winner after RBL had taken the lead.
"It was a good feeling to get the goal but it was all about the three points and topping the group," the Scotland Under-21 international told City's website.
"It means everything to top the group. We are the strongest team in the group for a second year and and I do think we are probably one of the strongest teams in the competition.
"The coach asked me to get on the ball and do my stuff around the edge of the box and that hopefully we would create chances and score goals and I think I did that towards the end of the second half."