Reading the rules for inspiration, you may be able to give yourself inspiration by targetting an ally who already has heroic inspiration.
In 2024 you can pass the inspiration when you receive it, but you can't grant it to an ally on the fly anymore.
So reading the rules strictly, you can give your whole party (6 people including you) inspiration at level 1, by just short resting three times in succession.
I am not sure that is the intend. And I think the feat is too strong used that way. Either it should be available at long rests only. Or it should state that the old inspirations gained by this feat vanish if you use it again.
So I will interpret the last line "you can affect a number of allies equal to your proficiency bonus" as the maximum number of allies who can have heroic inspiration you granted from that feat.