Maybe more clear:
Note that precision is the total number of digits, scale included
NUMBER(Precision,Scale)
Precision 8, scale 3 : 87654.321
Precision 5, scale 3 : 54.321
Precision 5, scale 1 : 5432.1
Precision 5, scale 0 : 54321
Precision 5, scale -1: 54320
Precision 5, scale -3: 54000
If value is 9999.988 and Precision 4, scale 2 then it means 9999(it represents precision).99(scale is 2 so .988 is rounded to .99)
If value is 9999.9887 and precision is 4, scale is 2 then it means 9999.99
precision: Its the total number of digits before or after the radix point. EX: 123.456 here precision is 6.
Scale: Its the total number of digits after the radix point. EX: 123.456 here Scaleis 3
Precision is the total number of digits, can be between 1 and 38.
Scale is the number of digits after the decimal point, may also be set as negative for rounding.
Example:
NUMBER(7,5): 12.12345
NUMBER(5,0): 12345
More details on the ORACLE website:
https://docs.oracle.com/cd/B28359_01/server.111/b28318/datatype.htm#CNCPT1832
Precision 4, scale 2: 99.99
Precision 10, scale 0: 9999999999
Precision 8, scale 3: 99999.999
Precision 5, scale -3: 99999000
Precision is the number of significant digits. Oracle guarantees the portability of numbers with precision ranging from 1 to 38.
Scale is the number of digits to the right (positive) or left (negative) of the decimal point. The scale can range from -84 to 127.
In your case, ID with precision 6 means it won't accept a number with 7 or more significant digits.
Reference:
http://download.oracle.com/docs/cd/B28359_01/server.111/b28318/datatype.htm#CNCPT1832
That page also has some examples that will make you understand precision and scale.
Source: Stackoverflow.com