Oracle 10g sga

Any ideas out there why the sga discrepancy?

1. Oracle 10.2.0.1.0
2. The SGA was inadequately sized… suggest 1480M
3. sho parameter sga
sga_max_size big_integer 1148
sga_target big_integer 1148

4. alter system set sga_max_size=1480M scope=spfile;
System altered

5. startup force
good

6. sho parameter sga
sga_max_size big_integer 1776M
sga_target big_integer 1776M

How did 1776M occur? why isn’t it 1480M?
and I did not have to do an “alter sga_target” and yet sga_target “automatically” changed?

I’m not unhappy about this as the intent was to increase sga_target, but I’ve done the sga alters on another server and did not run into this.

Thanks in advance,
Ed