@deepa.singh , It’s not error but the way you are handling calculation is not right approach.
You can achieve distinct count simply by using
distinct_countIf({aura_tran_key}, {rule_execution_status} = “TRUE”)
This will count aura_tran_key when one of the rule execution is found to be TRUE. You can refer this dashboard on Arena
This is based on problem statement you have provided. In case you need more assistance , please create a sample dashboard with sample dataset showing your problem state using Arena and post it here. (Details on using Arena can be found here - QuickSight Arena )