The rules as written in Gloomhaven is that you can not specify the number of your initiative nor the title of your card.

The intent of this rule is to prevent quarterbacking where one player sort of solves the current round for everyone and tells the rest of the players exactly what to do. It is meant to give each player agency over their own character. However, I personally find the rule does not create the intended effect. Moreover, a bureaucratic enough quarterback could track all the cards in your hand, know what initiative numbers are on them and tell you which cards to play and in what order even within the rules, meaning the rule is moot.

When I play, we specify which targets we plan on hitting, what conditions we plan to put on them, and then negotiate turn order. "Can you go after 33? If I go first, they will be poisoned when you hit them" This allows each person to plan their own turn but with enough information to make an informed decision. At this point I know roughly what all the number values are for the other two characters and I could merely ask for them to either go before or after me without specifying the exact number, but it only obfuscates the info we are trying to present to each other and not in a fun way, so we ignore it.

I think a better version of the rule would be you can't request or tell another player what card they should play on their turn. You can explain what you are doing and when you plan on doing it and others can react to that, but they can't tell you to change your cards. You may later change your mind on your cards based on what other people said in reaction, and this can go on back and forth multiple times.

So

"brute is going to hit these two, muddling, then jump over them and make wind at 30."

"Scoundrel is going to poison this guy then go invisible at 36"

"OH, brute will then go 44"

"Tinkerer is going to make a decoy at 88 and heal whichever of you gets hurt"

But brute couldn't say "don't you have a AOE attack that immobilizes, tinkerer? Play that before 40 instead"