Most likely every 14 days will increase 1 point from each feedback's within your trust network.
It increases every month by +1.
So how your trust score become +1 since it's not a month that you have got positive feedback

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However I am not saying you are totally wrong. I just noticed on my first score, after I didn't bothered to calculate it. You might get more clear answers from below quote. Perhaps first score reflect after two weeks then increase by every month.
It starts changing after approximately 2 weeks, theymos uses "round_up" for months.