That orange "+" block is an indication that the typed measure is too wide to fit into the column. You can tap the "+" (or really anywhere in the measure) to temporarily see the entire measure you've typed.
Options to squeeze more measure into the column: Make sure you've got "Minimize horizontal spacing" selected in chart settings, and going to fewer Measures per Line in settings will help, if you haven't already dialed that down. And of course the Chart Font Size setting. Hope this helps!