Is there a document describe the details of the export data?

[pingguokiller]

'13_UhCt8LGA': {'vid': '13', 'flg': 0, 'z': [], 'xy': [7, 66.286, 89.143, 22.857, 516.571, 73.143, 1078.857, 1005.714, 1081.143, 1058.286, 482.286, 1026.286, 91.429], 'av': {}},

The above is a part of the export data. I can't understand the meaning of the number '7' just after 'xy'.