Provisionally accepted means that the details you have provided are accepted and they are said to be provisional because the details you have provided in the application aren't verified officially. After, round 1 your documents will be verified if you qualify and after that you will get the status of Partially accepted and if you finally get allotted then you will get the update of Completely accepted.

For more information regarding MTS consider the link below:

https://competition.careers360.com/articles/ssc-mts

I hope this helps. Wish you a great eve!