Rollback Segment Question

Hey All,

Take a look at the results of this query. Why is it that rollback segment 23 (RBS23) seems to have all the extends?

They are all the same size, and sized identically, and we do not use any statements to assign rollback segments.......

SQL> select n.name,s.usn,s.extends ,s.wraps   2 from v$rollname n, v$rollstat s
  3 where n.usn = s.usn;

NAME                                  USN    EXTENDS      WRAPS
------------------------------ ---------- ---------- ----------
SYSTEM                                  0          0          3
RBS0                                   31          0        120
RBS1                                   32          0        117
RBS2                                   33          0        145
RBS3                                   34          0        123
RBS4                                   35          0        115
RBS5                                   36          0        143
RBS6                                   37          0        161
RBS7                                   38          0        177
RBS8                                   39          0        123
RBS9                                   40          0        147
RBS10                                  41          0        441
RBS11                                  42          0        208
RBS12                                  43          0        160
RBS13                                  44          0        142
RBS14                                  45          0        141
RBS15                                  46          0        129
RBS16                                  47          0        152
RBS17                                  48          0        136
RBS18                                  49          0        129
RBS19                                  50          0        175
RBS20                                  51          0        117
RBS21                                  52          0        186
RBS22                                  53          0        128
RBS23                                  54        683       1216
RBS24                                  55          0        135
RBS25                                  56          0        118
RBS26                                  57          0        347
RBS27                                  58          0        120
RBS28                                  59          0        129