Those aren't the splits that I would choose for myself. But then I have been to all 4 of the cities you mention in Belgium, many times.
I would take different amounts of time in some of these based on what I like to see, and what I like to return to time after time.
The only way really that I can help with duration in each of the cities is to know what it is that you are there to visit and see.
What appealed to you about Bruges? A boat ride? A walk or cycle to the coast? The Basilica of the Holy Blood? The Fish Market? Shopping? People watching? Riding in a horse drawn carriage? Strolling the back streets? The food? The Minnewater? The Roman ruins? The archery? Windmills? Bike riding on the cobblestones? Climbing the Belfry? Drinking Belgian beer? Drinking Gin? Seeing the Michelangelo? What?
See what I mean? How else can we help if we don't know which is important to you and which you don't care about. What attracted you to Bruges?
Same or similar questions about the other cities. And why did you want a day in Copenhagen?
Just for the record, if I were doing it, I would base in one place, probably Gent, and take the short train rides to Bruges, Antwerp and Brussels from there. They are all about the same length of train ride away, although Brussels may be fractionally faster. Unless I had a particular goal in Brussels - I usually don't - I would only change trains there if needed (probably on the way from Paris) and spend no further time there, certainly not with your short time frame, a day in Antwerp, a day in Gent, and the rest in Bruges. Frankly I'd probably skip one of those and take 2 in each of 2.
But please tell us what you hope to see and do.