Purchase Order Authorisation absolute limits

[tohoma_erp]

Hi all.
I am new to this forum and I just started to try webERP.

I am setting it up for a company in Indonesia using Rupiah currency and it requires quite a big number of PO authorization limit (>10billion). FYI, 1USD = ~10,000 rupiah.
When I entered 10billion (10,000,000,000), webERP change it to 2,147,483,647 (which only equivalent to 200thousands USD).

Is there any way to increase the limit, or just the limitation of the webERP?
If I have to change the code, appreciate if someone can provide pointer to what file/module to modify.

Thanks and regards,
iwan