Adjust order of calculation to prevent integer underflow am: 8929a8ef29 am: 0c87bce93e am: bf0219683e

Original change: https://android-review.googlesource.com/c/platform/test/vts-testcase/security/+/1953491

Change-Id: Ibaf70a75611ed914c51e89a9e196dcff3c269db9