I am using the MCD64A1.006 MODIS Burned Area Monthly Global 500m dataset to look at wildfire history over a certain area. I have downloaded the images from GEE and then uploaded them into Arc desktop. Within the images which display fire events, the pixels classified as burnt vary in their values. I am confused about what these values show. In some things I have read, it seems as though these represent the day of the fire, but the images are all for the first of each month so I don't understand how another temporal aspect really fits in. If anybody has used this imagery and could explain to me what the varying pixel values mean that would be extremely helpful!
The values in the MCD64A1 layer are the estimated dates of mapped burns.
Ordinal day of burn (1-366) for each 500-m grid cell, with 0 = unburned land, -1 = unmapped due to insufficient data, and -2 = water.
See more in the MCD64A1 User Guide.
I agree that this can be a bit confusing, when you have a monthly product, but you should remember that this data layer is intended for both ongoing monitoring and for historical analysis.