DB2 : Length of concatenated fields different -

below query gives 2 different wrong length same numbers ,in ibm db2 sql why there 2 different length same value ?

select    decimal(trim(cast(15 char(2)))||trim(lpad(cast(7   char(2)),2,'0'))||trim(lpad(cast(13 char(2)),2,'0'))),   length(decimal(trim(cast(15 char(2)))||trim(lpad(cast(7 char(2)),2,'0'))||trim(lpad(cast(13 char(2)),2,'0')))),   decimal(trim(substr(replace(char(current_date -1 days,iso),'-',''),3,6)),6,0),   length(decimal(trim(substr(replace(char(current_date -1 days,iso),'-',''),3,6)),6,0)) sysibm.sysdummy1 

these numbers not same value first 1 15713 , second 150713.