A couple quick questions regarding MTurk/SpeechPad transcription style guide

I'm looking over the style guide, and there's one thing I wanted to double check with you guys about. In the section for timestamps, this is what it says:

For 30 second and 60 second intervals, timestamps should be placed between sentences. If there is a long, complex sentence, the timestamp can be placed after the comma and before the conjunction. The timestamps may not fall at exactly 30 or 60 second intervals.

Based on the wording, I'm not entirely clear whether timestamps are meant to be used by default or not. The guide doesn't say. It just says that you should "read the customer instructions regarding the selected timestamping interval". I don't know if the part I quoted is meant to apply to all transcriptions or only those that require timestamps.

I haven't taken any of the tests yet because I'm not sure how many failures they allow, and I didn't want to try before I make sure I understand everything properly.