The deposit component of a Deferred Payment is always due immediately the Invoice is processed regardless of the terms on the Customer account.
The installations will be due x number of months away and are payable immediately on those dates - ie normal account terms do not apply.
So if a term of 6 months is specified with no payments for 1 month - there will be 5 installations due. The first will be due in 2 months time, then 3, 4 5, and 6 months.
The only statement layouts which correctly handle deferred payments at this time are Open Item and they will not list the installations due until they are due (ie until the time they are reported as Deferred).
Deferred payment terms were intended to give normally "cash" account holders the option to delay payment - much like an account with 20 day terms, and that those cash Customers would not normally get statements