Redundancy calculations

Spoke to a friend earlier who works part time and position is becoming redundant company offering 4 weeks per year of service. He has 4 years full time service and 4 years half time. My understanding is that this constitutes 6 years service and that calculations should be based on 6 years service which would give 30 weeks of FT Salary. The company are offering him 8 years service but using the half salary as the calculator which means he is being offered 32 weeks but only at half salary.

Can anyone guide us in this matter

It would appear from this that the employer is correct but I am no expert in the matter.