Results are varying with same query

Hi I stuck in strange issue with one of my query.

Formula : (28800/3600-(28382.6/3600-(1920/3600+1860/3600))) =

So, Input Equation:

= (28800/3600-(28382.6/3600-(1920/3600+1860/3600)))

= (28800/3600-(28382.6/3600-(0.53333333333333+1860/3600)))

= (28800/3600-(28382.6/3600-(0.53333333333333+0.51666666666667)))

= (28800/3600-(28382.6/3600-(1.05)))

= (28800/3600-(28382.6/3600-1.05))

= (28800/3600-(7.8840555555556-1.05))

= (28800/3600-(6.8340555555556))

= (28800/3600-6.8340555555556)

= (8-6.8340555555556)

= (1.1659444444444)

= 1.1659444444444

But I am getting 0 as output from my query, it supposed to print 1

select (to_char (NULLIF(GREATEST(coalesce(28800/3600,0) - (coalesce(28382.6/3600,0) - 
(coalesce(1920/3600,0) + (coalesce(1860/3600,0)))),0),0),'FM99,999,999,999'))::character varying as mydatas

Now, same formula and same query with different values working fine. please check following.

(28800/3600-(13552.24/3600-(900/3600+0/3600)))

Input Equation:

= (28800/3600-(13552.24/3600-(900/3600+0/3600)))

= (28800/3600-(13552.24/3600-(0.25+0/3600)))

= (28800/3600-(13552.24/3600-(0.25+0)))

= (28800/3600-(13552.24/3600-(0.25)))

= (28800/3600-(13552.24/3600-0.25))

= (28800/3600-(3.7645111111111-0.25))

= (28800/3600-(3.5145111111111))

= (28800/3600-3.5145111111111)

= (8-3.5145111111111)

= (4.4854888888889)

= 4.4854888888889

so my query also gives 4 as output

select (to_char (NULLIF(GREATEST(coalesce(28800/3600,0) - (coalesce(13552.24/3600,0) - 
(coalesce(900/3600,0) + (coalesce(0/3600,0)))),0),0),'FM99,999,999'))::character varying as mydatas

select ((NULLIF(GREATEST(coalesce(28800/3600,0) - (coalesce(28382.6/3600,0) - 
(coalesce(1920/3600,0) + (coalesce(1860/3600,0)))),0),0)))::character varying as mydatas

= select (28800/3600-(28382.6/3600-(1920/3600+1860/3600)));

= select (28800/3600-(28382.6/3600-(0.53333333333333+0.51666666666667))); -- False

= select (28800.0/3600-(28382.6/3600-(1920.0/3600+1860.0/3600)));