I worked for a company as a full time employee on a continuous contract for over 12 months (in 2018), working Mondays to Fridays. I was paid on a monthly basis with a basic salary + commission. After leaving the company, I realised they did not use the 713 calculation for the holidays taken during my employment (i.e. I was paid the basic monthly salary without deductions/adjustments even on for the days I had taken statutory leave).

They have now agreed to pay back the difference (only for the statutory days and not the additional annual leave days agreed in the contract), but we are in dispute in how it should be calculated. Both the company and I have a clear understanding of how the average daily wage is calculated, but we disagree on which figures should be included in the calculation of the total salary of the month.

Note: the company uses working days instead of calendar days when calculating wages.

My understanding of calculating the monthly pay is the sum of the following:
- Basic salary pro-rated for the actual days worked (e.g. $20,000/20 working days x 19 actual working days = $19,000)
- Commission (e.g. $10,000)
- Average Daily Wage as calculated using figures of the previous 12 months (e.g. $1,200 x 1 SH day)
So the total wages for the month would be = 19,000 + 10,000 + 1,200 = $30,200

However, their method of calculation includes part of the commission to cover the statutory payment (i.e. the commission for the month is pro-rated and included in my SH pay):
- Basic salary AND Commission pro-rated for the actual days worked (e.g. [$20,000 + $10,000] / 20 working days x 19 actual working days = $28,500)
- Average Daily Wage (e.g. $1,200 x 1 SH day))
Total wages for the month according to their calculation is = $28,500 + $1,200 = $29,700

If they work out that the Average Daily Wage to be used for that month (in this example, $1,200) is less than the average wage per day paid out for the month (i.e. basic+commission/working days = 20,000+10,000 / 20 = $1,425), they claim they have "overpaid" me. However, my understanding is that they made no adjustments for SH during my employment so the "paid" amount for the SH would've been the monthly basic salary (excluding commission) $20,000/20* 1 day SH = $1,000, which is less than the Average Daily Wage.

According to their calculation, during the entire employment period I was "overpaid" a total amount of over $8,000. This does not make sense to me because, wouldn't this defeat the purpose of the 713 Ordinance if I was "overpaid" even with the absence of using average daily wage to calculate my statutory holidays?

So, the question is, should part of the commission be 'deducted' to be included as part of the statutory payment when this was not explicitly stated in the employment contract?