Limit to three query over query tables

Limit to three query over query tables

Can you explain how the Query over Query Tables levels are calculated in producing this error? 
"The above query cannot be saved, a maximum of 3 levels of Query over Query tables only allowed."  

I have a ZohoCRM Opportunities table, a Query Table that pulls daily sales for business line 1, a Query Table that pulls daily sales for business line 2 and then a Query table that JOINS those two business lines to a fixed Projections table.  I don't understand why I'm hitting my limit of query tables...