It is entirely up to you and your potential supervisor to decide on an exact schedule (or to commit to more hours than this). We want to provide flexibility with respect to scheduling because we know that not every research project works in the same way. For example, it may make sense for you to work in the lab for 6 hours each week for 12 weeks (= 72 hours total) if you are working in a molecular biology lab where samples can be prepared at virtually any time, day or night, or if your research project involves literature searches or computer analysis. Alternatively, it may make sense for you to put in 8 hours of work per day for 9 days on your project if your project involves a concentrated period of data collection on, for example, plants in the wild.