Struggling to get my multisite domain mapping to work

It doesn’t matter what I try and do, every time I try and map a domain to one of my multisite sites, it just doesn’t work, I just get invalid all the time, or my A records are set up wrong. I’ve tried a number of different A records and Cnames now but to no avail,

All i want to do is use the domain mapping plugin so that my subdomain is reachable from another domain, please help