Master data and attributes?

Expert's,

Please go through this scenerio and answer the questions?

I have master data ZSTAT for this we have mainitaned the attribute called ZATT.

The data for these is not coming from source.So there is routine in UR which manipulates and updates the ZSTAT as I,N and T based on the conditions given in the UR.But Now If I look at the attribute ZATT I could see only I and N data.How this has maintained.This had done by our onsite folks.My doubt is How did we get only two values for attibute when we are having 3 values for Master data?

Points will be definitely assigned for the right answers?

Thanks in Advance.

Vasu.