So not quite as i thought. Total Solar Yield appear to be the Total Solar Yield in the preceeding time period chosen by the API. The two API calls below were made at the same time, one with 15 minute intervale and the other w 1 hours interval. As you can see the four 15 minute periods adds up to the same as the one 1 hour interval
{{{{0: array[2]
0: 1719810000000
1: 0.4011131227016449
1: array[2]
0: 1719810900000
1: 0.4798535108566284
2: array[2]
0: 1719811800000
1: 0.6598525643348694
3: array[2]
0: 1719812700000
1: 0.989460930228233}}}
{{{0: 1719810000000
1: 2.530280128121376}}}