Work it out by hand.
For the sake of magickal formulae, Crowley often changed a letter here and there to fit what he was trying to accomplish. As a magician there is nothing wrong with this, even if an orthodox speaker of the language would tell you its wrong.
An example of how you do Gematria:
YHVH = 10+5+6+5 = 26
26 is one idea, related to other ideas of the same number (though not every idea that has the number 26 for its gematria will relate, for example)
2 & 6 are seperate ideas
2+6 = 8 is another idea
26 = 12 is another idea
2 to the 6th power (222222 = 64) is another idea
Then... 6+4 = 10 another idea
6 and 4 another idea
6*4 = 24 another idea
6 to the 4th power (1296) is another idea-
Eventually you tend to hit a wall. Its important to understand the limit of Gematria, and when it has exceeded its usefulness. The idea is that, the more you analyze the numbers, the further away from the core idea (of 26) you are getting. This is also the da'athic danger of gematria, of knowing where the boundry between extracting hidden knowledge from an idea, and going off on a complete distraction.
You can then take YHVH, and spell it in full: YVD (20) HH (10) VV (12) HH (10)= 52, and on and on....