I stumbled across this post:
Is it ethical/legal to publish Master thesis manuscript as a journal paper?
Let me quote the top poster.
However, an MSc thesis is typically 50-100 pages long. A paper is (in a dense journal format) typically 8-12 pages long. Let's make a generous estimate for 20 pages in the thesis layout. So either your thesis is very thin, or the journal is very generous, both of which seems unlikely.
I'm currently finishing my master thesis. My professor likes the empirical results and told me I should orient myself to some journal articles in the respective journal he wants me to publish.
Why does a master thesis have to be 50-100 pages long?
I have written some parts of the thesis before and now that I am writing with the publication in mind I cut out >50%. I've realized that almost all of it was unecessary, boring "fluff" about definitions that every informed reader already knows or if not could find out much more easily online than reading my thesis.
Henceforth, the quote above concerned me.
I thought there is no problem in writing for a journal at the same time while writing the thesis. I plan to hand in my master thesis with approx. 30 pages. Everything is concisely explained. All other supplementary stuff will be pushed to the appendix.
I always found it particularly upsetting to have a minimum page number requirement. If its good, its good, or am I wrong?