Unable to manually convert on time to upgrade

User encountered below error upon cnverting ontime to upgrade

Findings:

Rule:
When you pay for an upgrade using ontime, you have to make sure the remaining ontime is at least enough for a week which is 7days.

Computation

to know if the customer has enought ontime that can be converted as an upgrade or not.

Downpayment for upgrade: 3,900 Kes

Daily rate : 30

Customer ontime left : 169 days
Ontime bonus (provided by user) : 33 days
Remaining ontime should have in the application (required) : 7days
Total days to be used in upgrade (169 - 33 -7 ) = 129 days
Convert to Payment: 129days * 30 (DR) = 3870 Kes only which is not enough to convert as upgrade as the downpayment for upgrade is 3900 Kes

or simply get the remaining ontime :

Customer ontime left : 169 days - Ontime bonus 33days =136days
136 days * Daily rate : 30 = 4080 Kes
4080 Kes - downpayment for upgrade 3900 Kes = 180 Kes
180 Kes / Daily rate : 30 = 6 days remaining Ontime only which is not enough

Solution:
Advise the user to ask the customer to pay for more ontime to be able to complete the task.