different cardinality

Hi,on 11.2.0.3

the same query has different cardinalty in Explai plan on two different databases. In step 15 for 1 DB I have :

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| Id  | Operation                          | Name               | Rows  | Bytes | Cost (%CPU)| Time     |                                                                                                                                                                                                   
---------------------------------------------------------------------------------------------------------  
|* 15 |     INDEX UNIQUE SCAN              | PS_VCHR_ACCTG_LINE |     1 |       |     1   (0)| 00:00:01 |
15 - access("A"."BUSINESS_UNIT"="B"."BUSINESS_UNIT" AND                                                                                                                                                                                                                                                     
SYS_OP_UNDESCEND(SYS_OP_DESCEND("VOUCHER_ID"))="B"."VOUCHER_ID" AND                                                                                                                                                                                                                                         
"B"."UNPOST_SEQ"="B"."UNPOST_SEQ" AND "B"."APPL_JRNL_ID"="B"."APPL_JRNL_ID" AND                                                                                                                                                                                                                             
"B"."POSTING_PROCESS"="B"."POSTING_PROCESS" AND "B"."PYMNT_CNT"="B"."PYMNT_CNT" AND                                                                                                                                                                                                                         
"B"."VOUCHER_LINE_NUM"="B"."VOUCHER_LINE_NUM" AND "B"."DISTRIB_LINE_NUM"="B"."DISTRIB_LINE_NUM"