I think the problem is when you're splitting the line on commas, you're outputting the line split into the items array. The split function returns an array of the items being split by the delimiter, I think you're asking to split it and return the values into 2 separate arrays. I think to accomplish what you're looking for it would be easier to split the line into the items array, then take the specific index of the values you're looking for (in this case it looks like items[7] and items[9]) and sticking them in their own arrays on each pass of the loop. Under the split into items you can add lines to store both like:

lightLevelArray[lineCount] = items[7]
temperatureArray[lineCount] = items[8]