XML/API Integration, price reduction?

[RytisT]

Hi. I'm trying to add a specific price (reduction) to product, like so: https://imgur.com/JueHjvC

but I'm getting my products and prices from API and I have no idea  how that 'specific price' option is supposed to be called. I've tried these:

$product->use_reduction = '1';

$product->on_sale = '1';

$product->reduction_type = 'percentage';

$product->reduction = "40.00";

$product->reduction_price = '40.00';

$product->specificprice = "40.00";

$product->specific_price = "40.00";

$product->specific_price_reduction = "40.00";

$product->reduction_amount = "40.00";

How would I go about updating reduction price/specific price in such way? Thanks.