Why am I taxed twice in a month?

My salary is divided into 2 payments per like I get my standard pay on the 15th of each month then all my allowances they follow on the 25th. So my question is why am I taxed twice in a month and why is the second tax deduction high than the deduction on the 15th?

You will pay tax on your mid-month pay as well as your end of month pay. Add the two together and use our
SARS income tax calculator to work out tax you should pay on your monthly earnings.