Understanding payslips

Hello, 

I'm having trouble understanding the differing figures on the payslip next to Hourly Rate: and CALC. RATE. 

For example -

On the payslip, in the top section, it will say:

Hourly Rate: $41.91

Then in the table, it will say: 

CALC. RATE: $40.07

Can anyone assist? 

Regards,

M