Yes, that time estimate is to run the full 64-item version with study, break for instructions, and full test session. You can shorted the duration by presenting fewer items. Feel free to download a free version and test it out with the 32 or 24-item versions (
https://faculty.sites.uci.edu/starklab/mnemonic-similarity-task-mst/). These shorter versions have proven to provide reliable estimates of recognition and lure discrimination, comparable to the 64-item version (Stark et al., Behavioral Neuroscience, 2015), but they do not provide enough lure items to break out performance by lure bin similarity.
I hope this helps!
Shauna