anchor.diff:  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:
  +Each of the `USAGE` items 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
  +* `rate`: We reused the `rate` field normally reserved for the `RECURRING` type to output the price of the tier
   
   Also, the `itemDetails` json field will provide some additional details:
   
  
positive.code: 
  ==== 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`. 
  
  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.
  
  ==== Agrregate 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:
  
  [source,bash]
  ----
  
negative.code: 
  Late Usage Data:
  
  If for some reason, there is some late usage reported in these past 2 periods, the system will include this delta. Depending on the type of usage and mode (e.g `AGGREGATE`) we will see one or several `USAGE` item for this period to reflect this additional charge. If the late usage is older than these past 2 periods, it is simply ignored.
  
  Missing Usage Data:
  
  