Conversion variables (eVars) allow Adobe Analytics to attribute success events to specific variable values. Sometimes, variables encounter more than one value before hitting a success event. For these cases, allocation determines which variable value gets credit for the event.
Ad Hoc Analysis has the unique ability to report different allocations for conversion variables: the default allocation, last allocation, and linear allocation. If Ad Hoc Analysis is your organization's primary reporting tool, having all conversion variables set to first allocation gives you all available allocation values.
Data Warehouse uses the same allocation settings as reports & analytics.