Custom field sorted by name and not a numeric value

-- HikaShop version -- : 3.1.1
-- Joomla version -- : 3.7.2
-- PHP version -- : 7.1
-- Browser(s) name and version -- : Chrome latest

I created a shop with tiles and each product has a custom field price/m2. When I sort products by this fields, the sort is A-Z, so it goes like
100, 129, 150, 40, 75
Is it possible to sort them by value: 40,75,100,129,150? How?

Thank you

It was possible - I changed in mySQL #__hikashop_product table this field from text to smallint and it works, I attach my table structure.