substring stopping things from working

ok ill put this is in steps as i feel that you guys are not understanding what i am meaning as i have dyslexia and find it hard to say what i actually meaning sometimes.

  1. i get my players health from ufps which is a value of 10f
  2. i divide it by 10 to get it to a number i can work with
  3. i use sub string to remove the 0. part of it so i am left with what is after which is 00
  4. when my health is lowerd it turns to 98 for example but it really is 0.98
  5. i take the same float that i put into the string and use it again to change the fillamount of a image

the problem is that when i include the substring to remove the 0. the rest of it does not seem to go i get this exeption ArgumentOutOfRangeException: Cannot exceed length of string.
but it should work as it = 1.00 and all im doing is taking away the 1. part i am using a substring of 2,3 to take the 00 out
im sorry if im being wrong here but i just dont get what you guys are trying to say to not use substrings even tho i want to, to learn them

So m_Player.Health.Get is a float from 0-10, and you want to display it as a string from 0% - 100%? Then:

healthf = m_Player.Health.Get () / 10;
Healthtxt.text = healthf.ToString("P0");

Still dont understand you. Why not just perform the division at the end?

It simply seems like you are trying to do this whole process backwards.