Under Northern Ireland, how many counties from Ireland stayed as part of the United Kingdom?

Okay, let's break down the counties of Northern Ireland. Historically, the island of Ireland was divided into 32 counties. When Ireland was partitioned in 1921, after the Irish War of Independence, the majority of the island became the Irish Free State, which later became the Republic of Ireland. However, six of the counties in the province of Ulster remained part of the United Kingdom, forming Northern Ireland. These six counties are Antrim, Armagh, Down, Fermanagh, Londonderry, and Tyrone. So, while the rest of Ireland gained independence, these six counties chose to stay within the UK. It's easy to get confused with the other numbers, but remembering that Northern Ireland was formed from six specific counties helps to nail down the correct answer.
Think of a dice. When you roll a dice, the maximum number you get is six, which is also the number of counties in Northern Ireland.