Pine Script function ta.change return value when use with math.sum

Question

first of all, I am writing Kaufman's Adaptive Moving Average (KAMA), and I am struggling with the calculation of Efficiency Ratio (ER).

First of all, let me explain the calculation of efficiency ratio.

ER = Change/Volatility
Change = ABS(Close - Close (10 periods ago))
Volatility = Sum10(ABS(Close - Prior Close))
Volatility is the sum of the absolute value of the last ten price changes (Close - Prior Close).

Here's what I did

    indicator('KAMA', shorttitle='KAMA', overlay=true)
    length = input(title='Length', defval=10)
    fastLength = input(title='Fast EMA constant', defval=2) //smoothing constant
    slowLength = input(title='Fast EMA length', defval=30) //smoothing constant
    source = input(title='Source', defval=close)

    change = math.abs(ta.change(source, length)) 
    volatility = math.sum(math.abs(ta.change(source)), length)
    ER = change/volatility

Since, I cannot see the return value of above calculation, so I am not sure whether my coding is correct. My question:

change = math.abs(ta.change(source, length))

1. Will this return the absolute value of the different between close price and price 10 bars ago?

volatility = math.sum(math.abs(ta.change(source)), length)

2. What will this return between:

2.1 The sum of abs different between current close - prior close doing this 10 bars back?

2.2 The sum of abs different between current close - close of 10 bars earlier.

Here's the image of calculation

Here's the reference of KAMA Calculation including spreadsheet