There must be a 30-day interval between the two exams of Si Pei.

This exam doesn't have to be 30 days apart.

Sipei is called the Canadian English proficiency index test. The interval of each test is 4 days, and the test results are valid for two years. You can apply for reconsideration within six months after scoring. Sipei is an English language testing system officially designated by IRCC of Canadian Immigration Bureau, which is mainly used to test the English application ability of people who wish to immigrate to Canada. There are two kinds of exams: the general exam of Sipei and the listening and speaking exam of Sipei.