Issue with H1, H2, H3 size in mobile devices

Hi:
I'm using Generate Press Premium and have an issue with the size of the typography with H1, H2, H3 text.
when I go to Customizer-Typography-Heading and choose the mobile icon, I had previously set the typography size to 25 px in Heading 1 (H1) but it's actually much bigger. It happens the same with H2 and H3.
Then I change the typography size to 26 px and then back to 25 px and it apparently sets the size to 25 px finally. Then I press "Publish" and leave the Customizer.
But if I enter again the Customizer and go to Customizer-Typography-Heading, even though the size of the Heading 1 (H1) is set to 25 px, the actual size is bigger again as if I hadn't published the changes I did before.
Is there any input field I should change?

Thanks in advance