How many hours a week a prisoner spends engaged in offender development hours and what activity this term covers.

I have asked John Ewing, Chief Executive of the Scottish Prison Service, to respond. His response is as follows:
Offender development hours were replaced with purposeful activity hours in 2009.
The amount of hours a prisoner is engaged in purposeful activity hours varies depending on individual prisoner needs and therefore would be different per prisoner and would vary on a weekly basis. Overcrowding is also a significant influence. Also remand and civil prisoners and those excluded on medical grounds are not legally obliged to undertake work.
Notwithstanding the above and based on the average prison population for 2010-11, prisoners spent on average 15 hours per week undertaking purposeful activity. If you exclude remand prisoners, sentenced prisoners spent on average 18 hours per week undertaking purposeful activity.
Purposeful Activities includes:
Work
Vocational Training
Education
Health support/promotion
Social Care
Links Services
Interventions
Physical Education
Addictions support/counselling