Unless clinicaltrials.gov just hasn't been updated yet officially we're still 28 days for the protocol. If that is the case 28 days is what will be submitted to the FDA. Data from 42 days would be a supplement to the report.

As long as the data stays blinded to the company it doesn't matter whether or not interim is done at 28 days and then later at 42 days also. If it is unblinded to the company at 28 days collection of data until 42 days can occur but the data from day 29 to 42 will not be considered unbiased.