Only way i can i think about that number is
If you are on 8/6 schedule thats avarage 17/18 days a month work .
Take 17 times 259.00 per day times 12 months. Out of the 30000.00 hiring bonus 5000 day 1 5000 after IOE 10000 end of first year , so ( 20000 first year ) Then 55.00 per diem per day times 17 days a month times 12 per year . This would come up to first year first officer pay 84056.00. Now there is tax on your pay and 20000 bonus .but not on per diem .