Minidiab is the brand name of a medicine called glipizide. Depending on individual cases, its dose ranges between 2.5mg to 20mg but can go up to a maximum of 40mg in rare cases. Its duration of action is up to 24 hours; hence it can be taken once in the morning. If more than 15mg is to be given per day, it should preferably be given in two divided doses i.e. 15-30 minutes before breakfast and 15-30 minutes before dinner. In your case it will mean 2 tablets in the morning and 2 in the evening.
Glucophage is the brand name of a medicine called metformin. Its speed and extent of absorption from the stomach is impaired to some degree in the presence of food. Hence it is better to take it before breakfast and before dinner.
Generally the recommendation is that both medicines be taken with meals. The idea is to ensure that meals are taken when medicines are taken so that the blood glucose levels do not fall if medicine is taken but food is not taken.