I have a problem with TEXT  is there a way to add text to another text but not to be combined together?

for example I have a dimension with certain size then I add to something below very close with different size for an explanation, but when I go to close to my dimension it includes the comment in the same text box, so everything becomes large as the text.

It must be something to avoid that, what I am doing for the moment that the text I make it as a block but it is not efficient

Please tell me what can I change in options so the text do not mix

thankx