When "+/- value" option is selected, new product price will be $5 + 10 = $15.
Having "Set fixed value" option checked will set new product price to $10.
Modifier page has four sections - Price Modifier, Wholesale Price Modifier, Quantity Modifier and Product Preview Properties Modifier.
Every section has "Modify..." checkbox. When it's checked, the add-on will make appropriate modifications, when unchecked - no modifications will be made.
Price Modifier (Special Price Modifier)
Check "Modify Price by" check-box to allow modifications. Set some numeric value and select one of three available options below:
You have some product with a price of $5.00. Check "Modify Price by" and specify 10 in the box on the left.
When "+/- %" option is selected, new product price will be $5.00 + 10% = $5.50.
You can specify the negative value (like -10) if you want to decrease product price.
Check "Smart Price" option for some additional price features. See below for more details.
Quantity modifier works in the same way as price modifier, except it's altering product quantity.
You can set In Stock, Out of Stock or leave it as is when "Modify Stock" option is not checked.
Advanced Modifier tab
Other Fields Tab allows you to modify other product fields. Set some value and check the appropriate box to make Mass Changer modify that field.
Here you may also specify the Description of the products, Meta information (meta keywords, meta title) etc.
Smart Price Options tab
This page has three sections - two for prices and one for testing.
Smart Price (Special Smart Price)
Smart price allows you to select smart marketing price like $9.99 instead of $10.00 or $24.95 rather than $25.00
Factor (Round) - round the price to be divisible by specified value. As for example, you'd like your price to be at $25, $30, $35 etc. but not $27 or $31. Set round value as 5 to automatically round the price.
When calculating new smart price the first operation is rounding and then delta value is used.
Combine "Delta" and "Round" values to get a smart price like $24.99 or $34.99 and so on.
Just type some value into Test Price box and see how it will calculate new prices.
The results page shows you all products you're going to modify with both old (current) value and new (modified) one.
You can review new values and edit them. You can change values in all columns, which have captions starting with "New" - e.g. "New price" or "New special price" etc. All other columns such as "Product Name",
"Product Model" or "Price" are read-only, do not try to change them.
By this moment all changes you had made were applied to some temporary set of products stored in memory. When you click OK button, all prices quantities and other modifications will be posted to your database to real products.
Please, check for more detailed information on Mass Product Changer functionality in the useful articles:
PrestaShop Mass Product Changer
How To Change Product’s Price and Quantity in a Few Seconds?
Check the following video tutorial to see how to operate with Mass Product Changer in practice: