Cbimportant can't handle key with numeric values 13 digit or more as Key

I have couchbase server 6.0.
cbimport was doing import to a bucket from a exported table from Oracle.
Oracle exported table has one column with 13 digit numeric values (no decimal) and export translates this to : 1.2220E+12
Couchbase document suggest it can handle number value with E notation :

However we we try to do cbimport with this column marking as key cbimport says all document ID successfully uploaded but Bucket didn’t fill and it just loaded few documents and stopped loading into bucket further .
the verbose didn’t give any error and neither CB Admin console . I was trying to load 3 Million data where only 421 records fill into bucket .
Also with E notation in Key causes the cbimport slow drastically … which is 200x slow .