QB Issue Resolution:

Add a subtotal line after the 25% discount & then add the 10% discount line.

Resolution for Issue 'How do I apply more than one discount so that the 2nd discount is taken off the 1st discounted total rather than the original total?' available: Yes (Solved).
Source: Intuit Community forum.

How do I apply more than one discount so that the 2nd discount is taken off the 1st discounted total rather than the original total?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for Quickbooks for Mac
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!

Error Recovery for Quickbooks for Mac [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.

Get 50% off Quickbooks Online

Click Here for 50% off!

Additional Support Options: