Can you share your site url so that i can check and let you know.
Bo here from Shopify Support!
I checked this with our themes team and this + symbol is there to signify that the price listed is the lowest price - there are more expensive variants. This is a default feature of the theme. Our team can add in a setting so you can toggle this on and off. To do so, you will need to be on a plan. Let me know if you are on a plan and would like our team to proceed with this. I can then email you to get this process started.
All the Best,