Does the reports display correct result when you run them independently ?
If you run them as regular report instead of graph, does the result is correct ?
This is the first thing to insure that they both run ok by themselves. It is not clear if you run them together (from a HTML page per example) or if they have no relation together.
What is the source of your data ? Do they share the same source from a DB, a HOLD file build from another process, ... ?
A COMPUTE is applied once the data as been extracted from the source (WHERE clauses applied) and once the BY fields are performed.
It could be possible that if your data is not extracted the way you thing it should, that the result differ from the expected result.
Posting your code may help to understand your issue.
WF versions : Prod 8.2.04M gen 33, Dev 8.2.04M gen 33, OS : Windows, DB : MSSQL, Outputs : HTML, Excel, PDF
In Focus since 2007