Do you have to tell your opponent how many cards you swap from sideboard between games?

Ruling: You do not have to tell your opponent how many cards you swapped from your sideboard between games.

Nuances:

• At High OPL and above, you can shuffle your sideboard into your main deck and pick 8 cards to remove, making it impossible for opponents to deduce how much you changed
• Your opponent may ask to count the cards in your sideboard for verification without looking at them