No. 'Not more than' does not necessarily imply 'less than'. 'Mere' never implies 'less than'.
"a mere month & a half"
It is amazing that all this has taken place a mere month and a half after Morsi took office.
Does it mean not more a month & a half? In other words, it means it didn't reach a month & a half.
mere adj - definition in American English Dictionary - Cambridge Dictionary Online
It emphasizes the smallness of the number.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.