Labour (direct indirect)

There is this question in BPP which I cannot understand
Jaffa Co employs two types of labour: skilled workers(direct labour) and semi skilled workers(indirect labour). Skilled labours are paid $ 10 per hour and semi skilled are paid $ 5 per hour.

Skilled labour works 20 hours overtime, 12 on specific order and 8 on general
Overtme is paid at time and quarter.
Semi skilled worked 30 hours overtime, 20 hours for a specific order at a customer’s request and the rest for general purposes . Overtime is paid at time quarter

On the answer i understood that 20 hour overtime is direct cost because he worked on SPECIFIC order.

But why we consider GENERAL overtime hour as a direct cost.

Please help me to understand this point. Thank you