How to CREATE GDG and use it in next step...?

Here in JCL first we are creating an GDG (+1) and using it in the next step what will be the generation number...?

//STEP1 EXEC PGM=IEFBR14
//DD1 DD DSN=CMAP054.TEST.GDGROUP(+1),
//       DISP=(NEW,CATLG,DELETE),
//       SPACE=(TRK,5),
//       DCB=(LRECL=80,RECFM=FB,BLKSIZE=800)
//STEP2 EXEC PGM=IEBGENER
//SYSUT1 DD DSN=  INPUT DATASET NAME,DISP=SHR
//SYSUT2 DD DSN= CMAP054.TEST.GDGGROUP(+1),DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSIN DD DUMMY
/*
//