why undoblocksdone is greater than undoblockstotal in v$fast_start_transactions

hi:

  i have a db of version 8.1.7.4 which is doing parallel transaction recovery now.

  i'm watching it's processing,now the following sql return strange result:

  select undoblocksdone completed,
       undoblockstotal total,
       undoblockstotal - undoblocksdone left, round(undoblocksdone / undoblockstotal * 100, 2) pct_completed
  from v$fast_start_transactions;

completed      total         left         pct_completed
  62499         61073     -1426    102.33

so how can i hnow when will the parallel transaction recovery finished?