Warmlight allows you to edit many parameters before you take a photo. If you don’t know how to access them - please check this guide.
The app’s Exposure settings combines both ISO and Shutter speed settings, that is why when you choose Exposure adjustment - it switches off adjustments for ISO and Shutter speed.
If you want more precise adjustments - you might consider editing ISO, Shutter speed and even Focus individually with a separate slider for each setting:
Hope this helps and please do not hesitate to contact us at firstname.lastname@example.org if you have any additional questions!