Last time Christmas Day fell on a Monday was 2017 and two of the three movies (Jumanji and Greatest Showman) opened early on Weds. Pitch Perfect 3 opened on a Friday with Thursday previews (presumably starting at 6 or 7pm?) and that ended up with 32% of its weekend on Monday. The other two movies did 52-63% of its opening weekend (which didn't have Thursday previews) on Monday. The reason I mention is this is that there tends to be a noticeable drop at the movies on Christmas Eve so if a movie like Aquaman tends to do a 2X mult from Friday (including Thursday) for the weekend, that's going to be even lower cause Sunday is Christmas Eve... and then it might only do 32% on Monday.
Without knowing any advance numbers from ticket sales, let's say (just as a hypothetical) that Aquaman does $19 million on Friday including Thursday previews... if that ends up with a 2X internal mult, that's $38 million for the weekend but then factor in Christmas Day that still gets up to $50 million. DC movies tend to be frontloaded to Thursday previews and that may be the case here, too... so doing some reverse math, if Aquaman does $38 million for the three-day, divide that by a 5.5X mult and that's about $6.9m Thursday which is what Aquaman would now need to do $50 million for the four-day. I think Anybody but You and Migration won't have to be so worried about being frontloaded to Thursday since they'll probably get a Christmas Day bump, esp since Migration is the only "kids movie"...
Just a little way too early morning math for you... don't say I didn't get anything for you on Christmas ;)