SQL - find ending number sequence

on 

SELECT * 
FROM (
    SELECT 
        T1.txt, 
        CAST(
            CASE 
                WHEN T1.Extended = 1 THEN 
                    CASE 
                        WHEN (T1.Highest64 - T1.Lowest64) = 0 THEN 1 
                        ELSE 
                            CAST((T1.NextRec64 - T1.Lowest64) AS DECIMAL(32, 16)) / 
                            CAST((T1.Highest64 - T1.Lowest64) AS DECIMAL(32, 16)) 
                    END
                ELSE 
                    CASE 
                        WHEN (T1.Highest - T1.Lowest) = 0 THEN 1 
                        ELSE 
                            CAST((T1.NextRec - T1.Lowest) AS DECIMAL(32, 16)) / 
                            CAST((T1.Highest - T1.Lowest) AS DECIMAL(32, 16)) 
                    END
            END AS NUMERIC(32, 16)
        ) AS percent_
    FROM NumberSequenceTable T1
) AS subquery
WHERE percent_ > 0.8;