Keensense is just a straight 1 for 1 addition to damage.
Also, HP does not increase in a 10-20-20 cycle. Starting at 10, It's 20 points each in most cases; with three instances of 10; two instances of 0; and one instance of 60 points (30). Note that I may have cocked up a little bit when transcribing the HTML values to a table.
Maximum companions (gets altered when you refresh your companion number):
- < 4 = 1
- < 7 = 2
- < 10 = 3
- < 15 = 4
- < 20 = 5
- < 25 = 6
- = 25 = no change (literally no change, not 6. Clearly unintentional)
- > 25 = 7