How to analyze the output of a Mamdani fuzzy inference system?

I designed a FIS (mamdani) and added some rules to it.

Have 2 labels on my dataset named 1 and 2. The problem is that when I evaluate data (just one row) it returns a number in output like 1.2555 or 1.5877.

I'm a little confused because its mamdani type and the output should be one of the labels, I mean (on my sample) output should be 1 or 2.

But why my output is a number like 1.2555 or 1.5877(as an example)? whats the relation between output and lables?

fis = addrule(fis,ruleList);

output =evalfis(fis,inputData);