Adjusted for day to day management (explorations on last bar of data etc).
Unadjusted for backtesting and older data.

A couple of ideas….

1. You have a system which has already decided to buy this stock at the next open. The methodology in your system is “Buy at next open price”. Today’s close is $22, so it still fits within the parameters of exploration to buy at next open. Overnight stock price dips, and actually it opens next session at $16.70. System would still assume you would take that buy as the filter condition on the day before at $22 was still met.

2. Similar to first idea… Today stock is trading at $21, but your limit buy order you have set up for tomorrow is at $16.70. Next session runs, low of the day drops down to $15, you get the fill at $16.70.

The stock NLOK announced a special dividend of $12 per share payable on the 31/1/20. The exploration on the 31/1/20 using adjusted data excludes the stock. I run the backtest from the 31/1/20 to 3/2/20 so on an unadjusted basis the stock is included.

Matthew, this is a monthly rotation system so I run the exploration on the last trading day of the month (after the close). Orders then entered for the first trading day of the next month (3/2/20).

I contacted Norgate in relation to adjusted & unadjusted data. They advised:

Open NDU’s “Data Viewer”.

Click on Tools > Data Viewer and select the Database “US Equities”. Then enter NLOK in the “search by symbol” box.

To flip between adjustment methods, click on Data Configuration > Stocks.

If you select “No adjustment”, you’ll see that the original (unadjusted) Close on Jan 31 was $28.42. If you elect to adjust for “Capital reconstructions and special distributions”, you’ll see that the adjusted Close on Jan 31 was $16.42.

To understand how adjustments are made, see the FAQ – When it comes to Price & Volume Adjustment for stocks, what events count as “Capital reconstructions” and “Special Distributions”?
https://norgatedata.com/ndu-faq.php#pricevoladjusts