In Kiwi's settings, you can change the header and sub-header text for the size chart pop-up. This would apply to all the size charts in the app. However, you can also change the text for specific size charts if you want.

In order to change the text in the pop-up header for specefic size charts, we have to go inside the Advanced Settings of that specific chart. Once you are in the desire size chart that you want to edit, just click on "More actions" and "Advanced Settings". 

On the Advanced Settings side screen, toggle OFF "Use Default Modal Settings" in order to get the necessary fields in order to edit the "pop-up modal header text" or "pop-up modal header sub-text". 

You can also use the syntax {{product.title}} for product title, {{product.vendor}} for vendor and {{product.type}} for type.