Gnat Miser — ruling 1

If multiple effects modify a player's hand size, apply them in timestamp order. For example, if you put Cursed Rack (an artifact that sets a chosen player's maximum hand size to four) onto the battlefield choosing your opponent and then put Gnat Miser onto the battlefield, your opponent will have a maximum hand size of three. However, if those permanents entered in the opposite order, your opponent's maximum hand size would be four.

Gnat Miser : règles, fonctionnement et interactions (MTG)

Gnat Miser is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Each opponent's maximum hand size is reduced by one.

How it works : Gnat Miser

Original English text — Wizards of the Coast / Scryfall

#1October 1, 2009· Wizards of the Coast
If multiple effects modify a player's hand size, apply them in timestamp order. For example, if you put Cursed Rack (an artifact that sets a chosen player's maximum hand size to four) onto the battlefield choosing your opponent and then put Gnat Miser onto the battlefield, your opponent will have a maximum hand size of three. However, if those permanents entered in the opposite order, your opponent's maximum hand size would be four.
No other card is named in this ruling.