Check out example codes for "loop backwards swift". It will help you in understanding the concepts better.

Code Example 1

for index in stride(from: 10, to: 5, by: -1) {
    print(index)
}
//10, 9, 8, 7, 6, 5

for index in stride(from: 10, through: 5, by: -1) {
    print(index)
}

//10, 9, 8, 7, 6, 5

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