I'll take the bet that the symbols are correct and all you're seeing is the scale difference between Sheet Layers and one of the Design Layers, or rather a zoom difference.
Sheet layers are always 1:1 - drop a 3" symbol on there and it will print out 3".
The Design layers can have any scale (right click on a design layer to explore 'active layer scale") - and when you drop your symbol on there it could well look tiny depending on your zoom factor at the time. Try measuring it with the dimension tool, or in top-plan view look at the rulers.
In my opinion it's best not to draw on the sheet layer but do all your drawing/ modeling on design layers and then create a viewport which will then reside on the sheet layer. You can set the scale of the viewport to whatever you like, even 1:1
so who's on?