IHS Refund Lower Than Expected

[revelation21]

I have received a IHS refund that is lower than I expect. I'm now trying to understand how refunds are calculated. Please see context below:

1) Original visas (T2G and one dependent) were issued March 11 2019, valid till April 4 2024. We paid a IHS surcharge of £2,000 per person as part of this application.
2) New visas (T2G and one dependent - changed at same time) were approved October 17 2020 and are valid till March 11 2025. A IHS surcharge of £1,800 per person was paid as part of this application.

We had 3 years and ~5 months left on our original visas. Therefore, I was expecting a refund of £1,200 (3 years) or £1,366 (3 years 5 months) per person.

Instead, I have only received a refund of £600 and the remarks indicate this is only for my dependent. My questions are as follows:
1) Should my expected refund per person be higher than the £600 I have received so far?
2) Do they usually refund the IHS surcharge separately for each applicant?

Please let me know if I am missing something or have the calculations wrong. Thanks in advance for your help!

[CR001]

The main thing you missed is that it was NOT necessary to apply for a dependent visa if the main applicant changed employers.

uk-tier-2-employer-sponsored-visas/when ... 98586.html

[revelation21]

Thank you. I didn’t miss that. My new employer insisted and I let them as they were paying all the costs (including the new IHS fees).

Any comments on my actual question re: the IHS refunds?