avg() on numeric ?

does avg() work on numeric ? it should, so, the more 
accurate one should be: on PG 6.5.1 ? 

please see below: (errors are on the last lines)
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create table salesreps (
empl_num        integer not null,
name            varchar (15) not null,
age             integer,
rep_office      integer,
title           varchar (10),
hiredate        date not null,
manager         integer,
quota           numeric(12,2), -- money,
sales           numeric(12,2) --money
);

test=> select * from salesreps;
empl_num|name         |age|rep_office|title    |  hiredate|manager|    quota|    sales
--------+-------------+---+----------+---------+----------+-------+---------+---------

105|Bill Adams   | 37|        13|Sales Rep|02-12-1988|    104|350000.00|367911.00
109|Mary Jones   | 31|        11|Sales Rep|10-12-1989|    106|300000.00|392725.00
102|Sue Smith    | 48|        21|Sales Rep|12-10-1986|    108|350000.00|474050.00
106|Sam Clark    | 52|        11|VP Sales |06-14-1988|       |275000.00|299912.00
104|Bob Smith    | 33|        12|Sales Mgr|05-19-1987|    106|200000.00|142594.00
101|Dan Roberts  | 45|        12|Sales Rep|10-20-1986|    104|300000.00|305673.00
110|Tom Snyder   | 41|          |Sales Rep|01-13-1990|    101|         | 75985.00
108|Larry Fitch  | 62|        21|Sales Mgr|10-12-1989|    106|350000.00|361865.00
103|Paul Cruz    | 29|        12|Sales Rep|03-01-1987|    104|275000.00|286775.00
107|Nancy Angelli| 49|        22|Sales Rep|11-14-1988|    108|300000.00|186042.00
(10 rows)


test=> select sum(quota) from salesreps;
sum
----------
2700000.00
(1 row)

test=> select count(quota) from salesreps;
count
-----
9
(1 row)

test=> select sum(quota)/count(quota) from salesreps;
?column?
-----------------
300000.0000000000
(1 row)

test=> select avg(quota) from salesreps;
ERROR:  overflow on numeric ABS(value) >= 10^-1 for field with precision 0 scale 1723

test=> select avg(sales) from salesreps;
ERROR:  overflow on numeric ABS(value) >= 10^-1 for field with precision 0
scale 1723