Confused by Engine Serial Number

[Martijn]

Hello,

I am confused ordering parts from my kubota dealer.

I got this information:
16264-73270 >=10001
16221-73270 >=110327

So use part code 16264-73270 when Engine Serial number is >=10001 and use part code 16221-73270 when engine serial number is >=110327.

I believe my Engine Serial number is XJ3489.
According to this site Serial Number Identification | Support | Kubota Engine Site that means X is year 1999 and J is month May. So my serial number is then 3489?

3489 is much lower then 10001. So it does not match any of the part numbers? My dealer says just go with 16264-73270, but I don't understand why. Also on the website Serial Number Identification | Support | Kubota Engine Site the serial number always seems to be 4 numbers. Is the parts catalog refering to another number?