Substract Value from Previous Row Grouped by specific Column

Hello Gurus,

Using Oracle 11 and having below data and

CREATE TABLE TOTAL_JOB (

  CODE VARCHAR2(10),

  JOB VARCHAR2(10),

  JOBCODE VARCHAR2(10),

  TOTAL number(10),

  SUBSTRACT number(10));

INSERT INTO TOTAL_JOB VALUES ('X1','47113','A1',6812,80);

INSERT INTO TOTAL_JOB VALUES ('X1','47114','A1',6812,100);

INSERT INTO TOTAL_JOB VALUES ('X1','47113','B1',3173,20);

INSERT INTO TOTAL_JOB VALUES ('X1','47114','B1',3173,25);

INSERT INTO TOTAL_JOB VALUES ('X1','47113','C1',0,20);

INSERT INTO TOTAL_JOB VALUES ('X1','47114','C1',0,25);

Using Below Query:

select * from TOTAL_JOB

SELECT TT1.code,

  TT1.job,