The production plan is clearly showing that you have more rows in production. No confusion in that.

In Dev...

364 HASH UNIQUE (cr=1208 pr=0 pw=0 time=783194 us)
545 FILTER (cr=1208 pr=0 pw=0 time=775342 us)
545 HASH JOIN (cr=1208 pr=0 pw=0 time=774670 us)
99432 TABLE ACCESS FULL CONTRACT_TRANS (cr=382 pr=0 pw=0 time=465 us)
18225 HASH JOIN (cr=826 pr=0 pw=0 time=359469 us)
1000 HASH JOIN (cr=445 pr=0 pw=0 time=108528 us)
46 TABLE ACCESS FULL CONTRACT_TRANS_GROUP (cr=223 pr=0 pw=0 time=48274 us)
675 TABLE ACCESS FULL CONTRACT_TRANS_GROUP (cr=222 pr=0 pw=0 time=51497 us)
99432 TABLE ACCESS FULL CONTRACT_TRANS (cr=381 pr=0 pw=0 time=182 us)
In Prod ...

364 HASH UNIQUE (cr=319722 pr=219 pw=0 time=78406184 us)
545 FILTER (cr=319722 pr=219 pw=0 time=78385884 us)
545 HASH JOIN (cr=319722 pr=219 pw=0 time=78384017 us)
675 TABLE ACCESS FULL CONTRACT_TRANS_GROUP (cr=222 pr=219 pw=0 time=328724 us)
2380118 NESTED LOOPS (cr=319500 pr=0 pw=0 time=71521450 us)
837 HASH JOIN (cr=603 pr=0 pw=0 time=315980 us)
46 TABLE ACCESS FULL CONTRACT_TRANS_GROUP (cr=222 pr=0 pw=0 time=48647 us)
99432 TABLE ACCESS FULL CONTRACT_TRANS (cr=381 pr=0 pw=0 time=100990 us)
2380118 TABLE ACCESS FULL CONTRACT_TRANS (cr=318897 pr=0 pw=0 time=70077111 us)
Can you please check which join or condition in production is fetching more data and investigate from there??

Thanks,