Difficulty understanding leave accrual, and how to adjust leave entitlement balances in Carry over and Year-to-date columns

I have been manually keeping records as I had issues with automatic leave entitlement accrual due to never having been able to understand how to correctly set up the leave entitlement categories for our permanent full time staff.  I found the article link below and I "think" I have now set up the leave entitlement categories correctly.

https://www.myob.com/au/support/myob-business/payroll/leave-and-entitlements?productview=Desktop

For now, I have used the Calculation Basis Hours per pay period, with the formula as follows:

20 (days annual leave per year) x 7.5 (working hours per day) = 150 hours

150 hours ÷ 52 (pay periods in a year) = 2.8846

Then to reduce balances when leave is taken, under the Linked Wages Category I ticked the applicable payroll categories e.g. Annual Leave Pay, Cashout annual leave in service, and Unused Annual Leave-ULT.

If I should be using the Calculation Basis Percent of Gross Hours, could someone please advise where the "Gross Hours" comes from.  Is it from the Hours in Weekly Pay Period? e.g:

If I now have the accrual set up properly, my second issue is that I am unsure how to correct the leave entitlement balances on the employee cards.  I can see that I can manually adjust the "Balance Adjustment" column, but I don't know how to correct the Carry Over and Year-to-Date columns.  For example, I need to correct the employee below to show that they have 968.2694 hours in the Carry Over column, and 31.7306 hours in the Year-to-Date column.  Is there a way to do this?

Any assistance or link to another article would be appreciated.

Thanks and regards

Narelle