interpret vacuum verbose output

hi all,

I'm trying to evaluate the frequecy to run vacuum
analyze on key tables.  so if anyone could help me to
interpret the output of vacuum analyze verbose output
that would be great. below is the output of one of our
major indexes.

INFO:  --Relation public.accounts--
INFO:  Index accounts_u1: Pages 1503; Tuples 231:
Deleted 55448.
    CPU 0.01s/0.14u sec elapsed 0.15 sec.
INFO:  Index account_u1: Pages 1997; Tuples 231:
Deleted 55448.
    CPU 0.01s/0.13u sec elapsed 0.15 sec.
INFO:  Index account_u2: Pages 2415; Tuples 231:
Deleted 55448.
    CPU 0.00s/0.14u sec elapsed 0.30 sec.
INFO:  Removed 55448 tuples in 2367 pages.
    CPU 0.04s/0.11u sec elapsed 0.41 sec.
INFO:  Pages 11266: Changed 4, Empty 0; Tup 231: Vac
55448, Keep 0, UnUsed 205434.
    Total CPU 0.12s/0.56u sec elapsed 1.08 sec.

thanks
Shankar

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