English does have 44 phonemes (this means that there are 44 possible sounds in the language). But for each of these sounds, there are a number of different ways to represent them in writing (for example 'f' can be written as f, ff, ph, gh). So the number of sound-letter combinations is around 170.
Of course, not all of them are equally common, so phonics focuses on the most common sound-letter combinations and our game covers around 40 of those. As our game is for beginners and only covers CVC words, we've left out some sounds that you don't find in such short words (for example the sound that si makes in division) and some vowels, such as the vowels in cure, ear, air.