Rate of change of sales (Variation) in an inflation economy

Given this data of Sales:

• Sales Sep-2017 \$ 10.000 (Values from Sep-2017. In other words, not adjusted)
• Sales Sep-2018 \$ 16.000 (Values from Sep-2018. In other words, not adjusted)
• Rate of inflation Sep 2017 - Sep 2018 = 70%

I want to compare Sales against Inflation. I know these 2 methods:

1. (Sales 09.2018 - Sales 09.2017 ) / Sales 09.2017 = Sales Variation

(16.000 - 10.000 ) / 10.000 = 60% = Sales Variation Sep 2017 to Sep 2018

Result: Sales were 10 points down compared to inflation. In other words, all the economy prices grew ten points over the rate of change of the sales.

2. (Sales 09.2018 * 1 - Sales 09.2017 * 1.70 ) / Sales 09.2017 *.70 = Sales Variation adjusted

Sales (16.000 * 1 - 10.000 *.1.7 ) / (10.000 * 1.7) = -5.88%

Result: Sales rate of change were -5.88 in adjusted values.

I can't find which is the difference between them, what implies each one of them. Which one is best to measure sales against inflation?