As far as I know, a x/y beat means you have x beats in a bar, where y is the prevailing time value. A real 6/8 has 6 beats, and a 12/8 has 12 beats.
Here's a little bit about time signatures for people who might be confused. The top number of a time signature
always refers to the number of notes (or rests) of the type indicated by the bottom number that are needed to fill a complete measure. In other words, a measure of 12 8 would contain the equivalent of 12 eighth notes or rests, etc. The top number also determines whether the time is simple or compound. If it's evenly divisible by 3 but not 3 itself, it's compound time. If that's
not the case, it's simple time, and then the top number also indicates the number of beats in each measure. If the time is compound, that is, a top number of 6, 9, 12, 15, etc., the number of beats in each measure is that top number divided by 3. The "compounding" concept come from subdividing each beat into 3 equal parts and superimposing them onto a system that's basically designed to work in groups of 2. In compound time, a beat is always represented by a dotted note of some type, for instance in 6 4 time, a beat is represented by a dotted half note. The feel of compound time can also be duplicated by using triplets in simple time. Note that after the first division of a beat into 3 in compound time, the next division almost always reverts back to 2, that is in 6 8, the next division of a eighth note is into 2 sixteenth notes.