What redundancy payment would this person get?

My friend had worked with her local council in England for 16years. When she became 60, 4 years ago she took her works pension and has her State Pension. She didn't break her service and continued to work there 3 days a week (formerly 5 days worked). She understands there could be different enhnacements from different councils but generally what is she entitled to in a redundancy situaton? Would the years she worked full time be taken in to consideration or would payment be based on what she works now? Also would this be on her total number of years employed (now 20) or just on the last 4 years?