Beacon of Hope affects any and all healing, including potions of healing
The beacon of hope spell states:
For the duration, each target [...] regains the maximum number of hit points possible from any healing.
The potion of healing states:
You regain hit points when you drink this potion...
Thus drinking a potion of healing would count as healing and thus it would be affected by the beacon of hope spell.
Your calculations are correct, a common potion of healing would heal 10, a greater potion of healing would heal 20, a superior potion of healing 40, and a supreme potion of healing 60.
If they had wanted the feature to work a different way they would have phrased it differently like they did with the Life Cleric's Supreme Healing feature:
Starting at 17th level, when you would normally roll one or more dice to restore hit points with a spell, you instead use the highest number possible for each die...
This feature restricts the maximized healing to spells, but beacon of hope has no such restriction and so it works even on non-spell healing like the potions of healing, and even non-magical healing like the Fighter's Second Wind feature or expending Hit Dice after a short rest:
On your turn, you can use a bonus action to regain hit points equal to 1d10 + your fighter level...
A character can spend one or more Hit Dice at the end of a short rest, up to the character's maximum number of Hit Dice, which is equal to the character's level. For each Hit Die spent in this way, the player rolls the die and adds the character's Constitution modifier to it. The character regains hit points equal to the total (minimum of 0)...
