I presume that you are on BaanIVx series....
There are various functionalities that update the ticst002 table.
If the sequence number is 0, then it is estimated values. Otherwise, it is Actuals.
Hours Accounting is one process. Among others, The table gets updated from tisfc010 table, for subcontracting rates. The overhead(ohcs), Machine Rates (mccs), Labor Costs(wgcs)..etc, are updated from the values maintained in ticpr150 (Operation Rates).
In ticst002, The Hrs stored are a consolidation of all the Hrs logged in that Operation/Work Center.
Remember, Its possible that there are different operations done in the same work center.
You might want to compare the hrs in tihra100 or run the report to print all the hrs per operation/wc from the hra module.
Hope this helps