This is the Chinese character for loyalty. The top part is the character for middle or center, and the bottom half means heart. It means to be loyal, you need your heart to be good and centered, and since Macbeth's own ambitions are chaotic and not goodhearted he wasn't truly loyal like Banquo.
Adinkra symbols are of African origin and reflect a system of human values that are universal: family, integrity, tolerance, harmony, determination, & protection among many others. Find a symbol that represents you.