Reflectance map black areas

Hi,
The reflectance map I generated has some black areas that appear white in the Pix4D interface. When I analyze these black areas using Python, the pixel values are -10000.
What does it means when the pixel values are -10000? How can I get the real value?
Thank you.

In PIX4Dmapper, a pixel value of -10000 typically indicates that the pixel is not valid or that there is no data available for that specific area.