The signature in Gmail for Android doesn't have to be set specifically; the same design as for desktop will be used. Since the signature is visible while composing an email, you can easily confirm that the correct one is applied.
However, if you have a signature entered in the Mobile signature settings, Gmail will use that instead. If you want to ensure that your mobile signature matches the one on your desktop, follow these steps to remove the mobile signature:
How to Remove a Mobile-Specific Signature in Gmail
Open the Gmail app on your Android device.
Tap the menu icon (☰) in the top-left corner.
Scroll down and select Settings.
Choose the email account you want to modify.
Tap Mobile signature.
Delete the existing signature and tap OK.
Once removed, Gmail will automatically use the same signature as your desktop version.
