Example 34 in “3.17 Evaluating $apply as an Expand Option” (http://docs.oasis-open.org/odata/odata-data-aggregation-ext/v4.0/cs02/odata-data-aggregation-ext-v4.0-cs02.html#_Toc435016591) says  that for following query:

GET Products?$expand=Sales($apply=aggregate(Amount with sum as Total))

 @odata.context in result should look like:

"@odata.context":"$metadata#Poducts(Salees(Amount)",

 There appear to be a few errors with the context:

• Typos in Products and Sales
• Amount instead of Total that is part of output
• Missing closing parens

 I believe the context should be:

"@odata.context":"$metadata#Products(Sales(Total))",