Tiered commission calculation in SQL - How to calculate?

I'm having the exact same problem as poster: tmyint had a few years back (a good few years)
View the original post and solution of poster: tmyint.

I trying to understand what the .01 in Scotts solution refers to, does any one know why in the CASE statement, inside the accepted solution he uses this "THEN .01"

I'll paste the exact code, in for quicker reference than the link

--create sample/test data
DROP TABLE commissions
CREATE TABLE commissions (
    tier TINYINT,
      flag TINYINT,
      lowValue DECIMAL(12, 2),
      highValue DECIMAL(12, 2),
      pct DECIMAL(3, 2)
      )
INSERT INTO commissions VALUES(0, 0,      0,     2147483647,  0.50) --default commission
INSERT INTO commissions VALUES(1, 1,      0,         100000,  0.50)
INSERT INTO commissions VALUES(2, 1, 100000.01,      250000,  0.55)
INSERT INTO commissions VALUES(3, 1, 250000.01,  2147483647,  0.60)

DROP TABLE revenues
CREATE TABLE revenues (
      empNum INT,
      gross DECIMAL(12, 2),      
      commissionFlag TINYINT
      )
INSERT INTO revenues VALUES(1111111, 300500, 1)
INSERT INTO revenues VALUES(2222222, 300500, 0)


SELECT rev.empNum, rev.gross, 
      SUM(CASE WHEN rev.gross > com.highValue 
               THEN com.highValue - com.lowValue + CASE WHEN com.lowValue <> 0 THEN .01 ELSE 0 END
               ELSE rev.gross - com.lowValue + CASE WHEN com.lowValue <> 0 THEN .01 ELSE 0 END END * com.pct) 
      AS [commission]
FROM revenues rev
INNER JOIN commissions com ON rev.commissionFlag = com.flag AND
      rev.gross >= com.lowValue
GROUP BY rev.empNum, rev.gross