Differences Between Mined Data And Queried Data : Association Rule

Dear all,

I have a table containing call records, and made a mining model from that table only. The model has 3 columns : calling_number, called_number, and target_operator, using Association Rule algorithm. The key is calling_number, input was operator, and predicted column called_number.

The result shows no rule, but there are results with item-set size of 1 (column) and 2 (column). On the top record of the result, SQL Server says there are 1891 support for called_number = 1891 and operator = 'INDOSAT'.

I queried the table with this query

SELECT DISTINCT calling_number
FROM call_records
WHERE called_number = '07786000815'
AND target_operator = 'INDOSAT';

It returns 2162 records instead of 1891. If I removed the DISTINCT qualifier, SQL Server returns 2159 records. Why is this differences with the result of mining?

Thank you,

Bernaridho