I got a little bit confused about how the 'Y' is pronounced in Roegadyn names.

Here it says:
Y: A long 'e' such as the 'ea' in 'eat' or the first 'e' in 'Steve'
Alyr (alder) would be pronounced 'ah-leer'
Blyss (blossom) would be pronounced like 'bleece' (rhymes with 'fleece')
But later on it says:
Pfym (five) would be 'fim' (rhymes with 'slim')
OR
The 'gin' in Swygyn (silent) would be NOT be pronounced like the drink 'gin' but like the 'gin' in 'begin'
Why isn't the first one pronounced as 'feem' or the second one as 'svee-geen'?
And how can I know when to pronounce it as 'ee' or or just an 'i' as in 'win'?

Thank you very much!