There are several ways to change the autocad label text size.
1. Open the label style editor with DST order > > select text label > >there are "text height" option, enter the height you want and it can be set up
2. Open the"label style" in "format" menu, the "label style" pop-up, click modification on the right side, select the "text" column and then chande the text height to 6 or so.
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