Clear mandate for what, exactly?

Mrs. May is sure there’s a clear mandate for limiting immigration, but it all depends who you voted for.

Johnson disagreed that the Brexit vote was mainly about immigration; Farage thought we were at breaking point, which Gove strongly disputed; Hannan told Newsnight that LEAVE had never promised numbers would go down; and Cummings offered voters the chance to take back a control they never had.

How come May decides that Farage is the one who matters?