You have to understand both how the jyutping romanization works (i.e. what sound 'bat' makes) as well as what the tones in Cantonese are. I'll let you read about the initials and finals (mostly consonants and vowels). There are some tricky ones: the 'c' in cat is pronounced more like an aspirated 'ts'.

There are six or nine tones in Cantonese:

high middle rising middle low rising low low falling

There are also three "entering" tones that some people don't distinguish at all, as they're sort of just the high/middle/low tones but short. I couldn't tell you whether they're really separate tones or just short versions of the first six.

You can see how the tone marks on the font line up with the tones here -- if you know them, the font marks are a reasonable guide.

For a rough guide of the sounds, the pronunciation key in Wikipedia does a good enough job.

https://en.wikipedia.org/wiki/Help:IPA/Cantonese

The font annotates each character using the Jyutping system for Cantonese pronunciation: https://en.wikipedia.org/wiki/Jyutping