Hydraulic fluid mixing- ATF and ISO46 oil

I’m flushing all the fluids in my old Hydra Mac and red fluid, assumed to be ATF, drained from my hydraulic reservoir. I was planning to replace it with ISO 46 hydraulic oil but am now concerned with any remaining ATF mixing with the ISO 46.

Should I return the oil and use ATF? Perhaps ATF is better for the machine anyway.

Thanks in advance.

Hydraulic fluid mixing- ATF and ISO46 oil