Sharepoint FullTextQuery doesnt work

Question

I have three scopes:

• scope A with rule include http: //mywebapp/lists/myList
• scope B with rule include FileExtenion aspx
• scope C with rule include http: //mywebapp/mysitecollection2/

some managed properties mapped to columns from myList, ows_contenttype, ows_created (Property1,2,3)

select title, url, description, Property1, Property2, Property3 from Scope() where scope = 'A' this returns 15 resullts

select title, url, description, Property1, Property2, Property3 from Scope() where scope = 'B' this returns 50 results

select title, url, description, Property1, Property2, Property3 from Scope() where scope = 'C' this returns 10 results

so why this query select title, url, description, Property1, Property2, Property3 from Scope() where scope = 'A' or scope='B' or scope='C' doesnt return 75 results ?? it returns 15 or some

FullTextSqlQuery sqlQuery = new FullTextSqlQuery (site); sqlQuery .ResultTypes = ResultType .RelevantResults ; sqlQuery .QueryText = sql ; sqlQuery .TrimDuplicates = true; sqlQuery.EnableStemming=true; ResultTableCollection results = sqlQuery .Execute();