First time i am trying to setup the plugin since i have it so forgive me if this is asked before.
In settings i can set default fee per 24 hours and it calculates using a formula. If i set 2 euro per 24 hours it sets 5.29 euro for 1 week.
Is there a way to set formula to count the same price per 24 hours so 1 week will be 14 euro, 2 weeks 28 euro ...instead of 5.29?
Thanks

Click on box and edit price 
Editing parent will update children as well.
Formula is somewhere in functions.php, just default values here

@MB Themes

if i set 24 hours to 1 euro my expectation is that it multiplies the amount 7 times  if i set it to 1 day and 1 week but that's not the case....
Like i said it's only the first day i am playing with this but i have to since sms payments is not supported anymore with fortumo/boku

Such formula would not make sense. You want users to pay more than they originslly wanted 

@MB Themes
I can confirm the issue.
If you set the price for 1 day to $2, then for 1 week the total is $5.29.
In this case, the correct multiplier would be $2*7= $14

What's the logic behind this? Discount for longer duration?

If so, then it would be nice for us to be able to set the discount based on a percentage setting.
For me, the way it is right now is a bit too much.
1 day - $10
1 week - $26.46
It's like you're ripping yourself off!

@MB Themes

It's not about ripping of someone it is only correct that if you have to pay €2 every 24 hours that the logic would be they have to pay 7 times the same amount every 24 hours so one week would be €14.
In situation it is now who's ripping who? 

Thanks @Tango to confirm the issue 

It's a bit like you're ripping yourself off, as the discount for 7 days vs 1 day is huge!
If you set 1 day to $10, then for 1 week it's $26.46 
You, as the site owner, are at a loss.

I understand to do a bit of upselling, and make the customer spend more money, but not with 62% discount

I would say a 15-20% discount would be okish, but still the best way would be for us to be able to set the upsell discount amount in the settings.

Correct! It would be nice to have the option for a discount in settings but i understand that maybe this is to difficult to create short term.
If it's working the correct way so €2/24h would become €14/1week then it would be nice for now 

I think it is solved but needs some testing. In functions.php from plugin starting in line 2064
// HOURS UPLIFT FOR CALCULATION OF DEFAULT 24H FEE TO DIFFERENT HOURS
function osp_hours_uplift($fee, $hours = NULL) {
  $price = $fee;

  if($hours <> '' && $hours > 0) {
    $days = $hours / 24;

    if($days < 1) {
      $price = $fee * pow($days, 1/4);
    } else if($days > 1) {
      $price = $fee * pow($days, 1/2);
    } else {
      $price = $fee;
    }
  }

  return $price;
}
Change 1/4 and 1/2 to 1 delete the delimiter and it seems like that is solving the problem...
// HOURS UPLIFT FOR CALCULATION OF DEFAULT 24H FEE TO DIFFERENT HOURS
function osp_hours_uplift($fee, $hours = NULL) {
  $price = $fee;

  if($hours <> '' && $hours > 0) {
    $days = $hours / 24;

    if($days < 1) {
      $price = $fee * pow($days, 1);
    } else if($days > 1) {
      $price = $fee * pow($days, 1);
    } else {
      $price = $fee;
    }
  }

  return $price;
}

Discount ( Full price per 6hrs / 12hrs/ ... ) can be set in plugin itself per category and per period.
If you don't want a discount it counts the normal fee per day...

To be continued :-)