Records representing items in a dimensionally-modeled fact collection are assigned to bins. A count-based portion of a user interface receives user bin assignment specification of the records based on user-specified counts of records. Actual counts for bin assignment are determined by constraining records having a same data value at a specified particular dimension to be within the same bin. A user-observable indication of the determined actual counts is provided. The user interface may include a value-based portion. The value-based portion of the user interface may be operated to receive user indication of bin assignment specification of records based on user-specified at least one value at the particular dimension. Determining actual counts includes reconciling the user indication of bin assignment specification in the count-based portion with the user indication of bin assignment specification in the value-based portion.