Does ADGM employment law calculate end-of-service gratuity differently from UAE mainland rules?

I have been working for a financial services firm registered in the Abu Dhabi Global Market (ADGM) free zone for the past four years on a fixed-term contract that has been renewed twice. My contract is now ending and my employer is calculating my end-of-service gratuity using what they call 'ADGM Employment Regulations' rather than the federal UAE Labour Law. The numbers they have given me are noticeably lower than what I calculated using the standard mainland formula. I am a British national on a work visa tied to this employer. I want to understand whether ADGM has its own distinct gratuity framework, whether my employer's calculation method is legally correct, and what dispute mechanism is available to me if I disagree with the final settlement figure.