anchor.diff:  
   ==== Consumable In Arrear Mode
   
  -In this mode, we are going through each tier level to compute the price based on the tier price and quantity. As described prevously, we support both `ALL_TIER` and `TOP_TIER` `TierBlockPolicy`. 
  +In this mode, we go through each tier level to compute the price based on the tier price and quantity. As described prevously, we support both `ALL_TIER` and `TOP_TIER` `TierBlockPolicy`. 
   
  -We can configure the invoicing system to output one item per tier, or one aggregate item for all tiers. The section below will consider a use case of `ALL_TIER` policy, but the idea between aggregate or detail mode remains the same.
  +We can configure the invoicing system to output one item per tier, or one aggregate item for all tiers. The section below will consider a use case of the `ALL_TIER` policy, but the idea between aggregate or detail mode remains the same.
   
  -==== Agrregate Mode
  +==== Aggregate Mode
   
  -In the aggregate mode, we will see one `USAGE` item with the aggregate amount across unit and tiers. The `itemDetails` json will summarize the usage on a per tier basis and per unit basis:
  +In the aggregate mode, we will see one `USAGE` item with the aggregate amount across units and tiers. The `itemDetails` json will summarize the usage on a per tier basis and per unit basis:
   
   [source,bash]
   ----
  
positive.code: invoice item -- and the aggregate amount is computed by summing the sum amount. In order to activate this mode, one needs to set
  the system property `org.killbill.invoice.item.result.behavior.mode` to `DETAIL`.
  
  Each of the `USAGE` item will contain the following fields:
  
  * `quantity`: Quantity consumed for the unit (type) and on the given tier
  * `rate`: We reused the `rate` field normally reserved for `RECURING` type to output the price of the tier
  
  Also, the `itemDetails` json field will provide some additional details:
  
  
negative.code: sections, each usage section is billed independently: As a result, we may see one or several `USAGE` invoice items per invoice,
  each associated with a given subscription, usage section and billing period.
  
  Regarless of the usage type the following basic fields will always be seen:
  
  * `planName`: The name of the `Plan` in the catalog
  * `phaseName`: The name of the `PlanPhase` in the catalog
  