When you create a big matrix (more than 15 columns and/or more than 20 rows), only part of the matrix is displayed at a time. This is done to spare the loading time and server resources.
Map navigation Matrix map will appear in the right top corner of the matrix screen.The green highlighted area is the part of the matrix that is currently displayed. Click on any cell on the matrix map to move to that part of the matrix.
Arrow navigation Up/down/right/left arrows will appear around the matrix if there are more cells in the corresponding direction. Click on the arrow to move one block up/down/right/left. By block we mean the current number of visible columns/rows. For example, if you have a matrix with 40 rows and rows 1-20 are currently displayed, the next block down will be rows from 20 to 40.