About the null values

Originally, I had used SRTM and GETASSE30 DEM. And I try to use Copernicus 30m DEM lately for interferogram. But that had many null values more than GETTASE30 in phase imageries. So I confirmed ‘No-Data Value’ at the properties. Copernicus 30m DEM had been had 0 ‘No-Data Value’. And I checked ‘No-Data Value’ at GETASSE30’s properties in order to compare with them. GETASSE30 has had -9999 ‘No-Data Value’.
Does ‘No-Data Value’ make a problem that is many null values at the images?

Thank you!

The question is edited with 2 screenshots

COP_30m_properties GETASSE30_properties

maybe you can illustrate your question with some screenshots.