Realizing that the 70 year exile to Babylon was nearing completion, Daniel humbly prayed for his people. His prayer was answered by Gabriel who gave him a prophecy of what was to happen to his people. During this discussion there is a chart with a summary of the standard interpretation of the 70 weeks. https://www.addeigloriam.org/commentary/ot-prophets/seventy-weeks-of-daniel.htm