Since the given table is an array, with a numerical index, using a for loop you can just do this:

local array = {1, 2, 3, 4, 5, 6, 7, 8}
-- Half of the array gives the middle
-- Meaning #array / 2 = 8 / 2 = 4
-- Note: odd numbers will require rounding (to give an integer)
local startPosition = #array / 2
for i = startPosition, #array do
print(array[i])
end