Why does my FTP go up +1 per ride/day?

Is this actually an algorithm calculating something, or just a typical progression/decay calculation being applied to the account?

Xert uses your historical data and tracks the relationship between low/high/peak training loads and your fitness signature. When you complete an activity, your training load increases and the slight change in fitness parameters (TP/HIE/PP) is meant to display this. Cheers!