It means to assume or believe, I guess
Although people sometimes use these expression interchangeably, there are 
subtle ... "I assume they left an hour ago" means that I know that their plan was to 
leave an hour ago and I am taking it for granted that things went... [DOC] [TLE] What is the difference in meaning between Assume & Suppose ... [PAR] May 6, 2014 ... What is the difference in meaning between Assume & Suppose.