SQL & PL/SQL

I have written the below query to find records with more than 2 decimal places, but it is returning records with decimal places 1 & 2. 
The datatype of the AMT column is NUMBER (without any precision).

SELECT amt  FROM amount_table
 WHERE substr(amt, instr(amt, '.')) LIKE '.%'
       AND length(substr(amt, instr(amt, '.') + 1)) > 2

Output:-

AMT

*41591.1*
*275684.82*
*64491.59*
*3320.01*
*6273.68*
*27814.18*
*30326.79*
131.8413635
162.5352898
208.5203816
8863.314632
22551.27856
74.716992
890.0158441
2622.299682
831.6683841
*1743.14*
2328.195877
3132.453438
5159.827334
3.236234727
37.784

Thanks