Double kickstand doesn't reach the ground

Hi everyone! I just finished my new old 90s mtb and I decided to put a double kickstand, an Ursus Jumbo, but there's about 1cm-ish between the feet and the ground, so the bike is not fully sitting on the kickstand. How should I gain this 1-2cm of height? I'm assuming I have to place a spacer between the frame and the kickstand's body itself? Thank you guys!