Please reach me out via email with your store URL.
I'm Miles from the Social Care team at Shopify. Would you prefer to remove the pop-up entirely, or change the discount? You can do either and I'll walk you through what you need to do.
Pop up's aren't natively built into Shopify, which means it's likely you have an app installed creating the pop-up or had custom coding added. If it's an app, you'll need to access it in the "Apps" option on your sidebar menu in your Shopify Admin. Depending on the app there may be different ways to edit or remove the detail, so if you do get stuck, you'll need to reach out to the app developer directly in order to remove the pop-up.
Having pop up discounts are a great way to encourage customers to purchase from your store. From your screenshot it looks like you're offering the discount for free, but did you know you can set up email marketing and incentivise customers to sign up to your newsletter and receive a discount code from there? You can check out apps like Seguno and Klaviyo which are great options for automated emails when your customer signs up to your newsletter.
We also have Shopify Email which is our built-in email marketing option. To use Shopify Email, you need to have an online store with Shopify, and to have the Online Store sales channel installed. If you want to send emails to your subscribers using Shopify Email, then your store needs to have a paid Shopify subscription plan with a payment provider set up. If your account is on the trial plan, then you can create email messages, and send test email messages to yourself using Shopify Email, but not to your subscribers. You can add in Shopify Email here.
Please let me know if you have any questions at all.