Rule clarification needed: Inspiration spent on attack roll

[Nikaea]

Hello, forum users. I need a wording/rule clarification regarding Investigator's Inspiration ability, because well, I'm not so good at English; need you people's help to understand it better...

It is written that "Inspiration can also be used on attack rolls and saving throws, at the cost of expending two uses of inspiration each time from the investigator's pool."

What Im getting confused is... If I spend single use of (two Inspiration points spent, but used only once that round) Inspiration to boost attack, do I get boost on a single attack roll made in that round, or on all of the attack rolls (provided that I have high enough BAB) made in that round?

Thank you for your time and have a nice day.

[Jeff Merola]

Single attack. You have to spend 2 points for each attack you want to use Inspiration on (or 1 if you have either an Inspired weapon or the Combat Inspiration talent).