Tier 2 Dependant visa

I am submitting an application for my wife to join me in UK, we are planning to travel on 12/05/2024. My tier 2 visa ( 5 years route) will expire on 17/11/2024.
When I applied my visa for myself, I chose more than three years.

Now, when applying for my wife as dependant, looks like the system doesn't account that when she joins me it will be less than 3 years for her. Actually, there is no option to chose which route for her.

The IHS successfully recognised that the duration for her is equal to or less than 6 months. Therefore, the system for IHS didn't charge fees.

However, regarding the application fee, the system shows that I have to pay 1872 USD. This fee is for more than three years, but my wife should be considered as less than three years. Since my visa will expire on 17/11/2024.

In the application, there is a questions regarding the length of the main applicant CoS grant. here I answered it as more than three years. since it asks about me.

Note: what is written in my CoS is more than three years.

I tried another application where I answered this question with less than three years, the fee dropped to around 860 USD.

In my case, does my wife has to follow the main application length of CoS ?
When answering this question, should put the remaining of my CoS time, or the original length ?

If I paid 1872 USD, and it turned that it should be 860 USD, do I get a partial refund ?