Tkprof "Parsing user id"

Hello,how can be identified the "Parsing user id" shown in tkprof output?

For example, let's take this tkprof ouput:

SQL ID: 9r7apbc0cdx6n Plan Hash: 3209728838

SELECT PLA.FLGLLRSEL
FROM
 TALU_PLAESTUDI PLA   WHERE PLA.CODALF =  :b1


call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        1      0.00       0.00          0          2          0           1
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        3      0.00       0.00          0          2          0           1

Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 45056
Number of plan statistics captured: 1
(...)

When I query dba_users, there's no user with id 45056:

select * from dba_users where user_id=45056;