Haha don't worry! It's always good to ask. Congratulations on starting down the path!
I think it's probably best to let the time organically grow, but do be sure to push yourself slightly so you don't get stuck in one spot. A timer is a good idea if you find yourself wanting to peak at the clock; it can help you to be determined and say, "I will sit until this bell rings no matter what." Otherwise that chapter is a really good resource, as is the entire book. Good to see you reading it!
May your practice be successful!
Gain and loss, status and disgrace,
censure and praise, pleasure and pain:
these conditions among human beings are inconstant,
impermanent, subject to change.
Knowing this, the wise person, mindful,
ponders these changing conditions.
Desirable things don’t charm the mind,
undesirable ones bring no resistance.
His welcoming and rebelling are scattered,
gone to their end,
do not exist.
- Lokavipatti Sutta