Well, it seems that this new profile you created is a duplicate. Thomas Gleason was already in WikiTree at https://www.wikitree.com/wiki/Gleason-1987
. It looks like you didn't discover the duplication because you were using a radically different birthdate for Thomas when you created the profile. The other profile cites the book you are using, and also some primary sources that confirm the information in the book. The book is a secondary source from long ago, but it looks like the authors/compilers did good work, even if they didn't cite sources the way we would do now-a-days. Although this man wasn't a PGM migrant, he's in colonial Massachusetts, and the page https://www.wikitree.com/wiki/Space:Puritan_Great_Migration_Project_Reliable_Sources
is a good source of guidance on reliable sources for colonial Massachusetts.
The profile for his wife is also a duplicate. I've proposed merges both both of them. The good news on this is that the merges will instantly connect you to a bunch more ancestors and relatives. And to avoid duplicates in the future, I strongly recommend that you use WikiTree name search to see if the early ancestor you are working on is in WikiTree already (many of them are). I usually run a name search, then sort the results by date and skim the list to see if there any results in the right approximate date and time. In spite of my best efforts, sometimes there's a duplicate that I failed to find, but searching in advance avoids a lot of merges.