Only 1 user selected microflow expression

Hello ! Im following the Create an App with Advanced App Building Learning Path and I’m stuck in the second module, in lecture 2.2.1  creating the microflow. My question is , how can I create the expression “only 1 user selected” for the decision ?  When I put $NumberOfUserRoles =1 it shows “unknown variable” … Thank you in advance !
1 answers

Please verify that you have followed the previous steps of microflow creation and that your microflow receives a parameter of TeamMember. Then a list of UserRole is retrieved. Then a count activity is used to count list which gives the variable “NumberOfUserRoles “. Attached image of microflow in 2.2.1 is available for reference. 
Unknown variable normally occurs when variable is not in scope. This could be if variable is never declared or the microflow path shown by arrows does not follow correctly. The variable is available along the lines/arrows i.e., flow of the microflow logic