For UK, is the allowed maximum of 180 days in one year or per stay?

I have a long term (2-year) type C business visa to the UK. From the website and other resources, it says that:
If you can prove you need to visit the UK regularly over a longer period, you can apply for a visa that lasts 1, 2, 5 or 10 years. You can stay for a maximum of 6 months on each visit.
This gives you unlimited entry into the UK during the visa’s validity - not to be confused with being allowed to stay for 1, 2, 5 or 10 years.
You are only allowed to stay in the UK for up to 180 days during each stay, unless the visa expires before the 180 days - as indicated by the ‘valid until’ date shown on the visit visa.
But when I contacted the customer support, the reply I got was:
With regards to your query, you can spend up to 6 months in any 12 month period in the UK. I hope this answers your query.
We strongly recommend not to book prepaid travel and accommodation before receiving the visa.
So I am confused about the "180 days during each stay" vs "180 days in 1 year of stay".
Could someone help me with that?
Pictures about "For UK, is the allowed maximum of 180 days in one year or per stay?"



Is the UK 180 day rule per visit or per year?
Visit visas allow stays of no longer than 6 months (or 180 days) per visit. Visit visas can be valid for long term periods (1 year or more), facilitating multiple visits. Additionally, those using visit visas are in general more limited in the activities they are permitted to undertake while in the UK.What is the 180 day rule UK?
If you've spent time outside the UKYou must have spent no more than 180 days outside the UK in any 12 months. If you think you're affected by this rule, the Home Office has guidance about how to calculate your time in the UK ('continuous residence').How many times can I visit the UK in a year?
There is no limit on the frequency of visits or specified maximum period visitors are allowed to spend in the UK in any 12-month period. However, if you spend more time in the UK than in your country of residence the Immigration Officer may have grounds to believe that you live in the UK.How many days in a year can you stay in the UK?
There is no specific day-count limit to the time a visitor can spend in the UK. This section of the guidance addresses the question directly... There is no specified maximum period which an individual can spend in the UK in any period such as '6 months in 12 months'.Check you do not overstay in Europe when travelling from the UK - Online Period of Stay Calculator
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Mikhail Nilov, Engin Akyurt, Rakicevic Nenad, rovenimages.com