06:30-02:30 (note the 0!) means 6:30 am to 2:30 am the following day. Anything in pm would be +12 hours. 6:30 pm becomes 18:30; 2:30pm is 14:30. Using this format you want 06:30-14:30 which is 8 hours.

This format is important because it actually solves the problem you are trying to explain (am/pm). Regularly I need to give EST database timestamps for a PST server cluster while living in another timezone myself and speaking to someone in India which is :30min difference in time zones and trying to account for daylight savings. Removing am/pm just makes it easier to track what happens in different places without looking at the wrong time window. Time math is messy and stupid, be specific by using 24 hours instead of 12