VAT adjustment tax

Hi,

When making a VAT adjustment it asks for a "Tax rate". What exactly should be selected here, since there shouldn't be VAT on a VAT adjustment? The two changes I'm making is increasing the following lines with adjustments:

• VAT on Standard Rate Goods and Services - Block 4
• Other Adjustments - Block 12

Also, why are the percentages shown invalid? South Africa's VAT rate is 15% and not 14%.

Thanks.