filed is set to initial automatically

hi,

when i try to create a table with 4 fileds with MANDT KUNNR as the key fields, the are automatically set to initial values...but when i generate the table maintainence generator and try to maintain the table , i could maintain values for KUNNR ..but i cant maintain values for MANDT...this is happening in the development system..can anyone help me in resolving the problem...based on this table i need to write a program which selects KUNNRs for a client and execute the statments...thank you..

challa