Two screenshots below, the first shows the intended addition which resulted in "2 + 3 = 23" while the second shows "32 + 48 = 80", yet other than the data-types the syntax is identical. At entry to sub "UpTheGrands, text boxes: tbNewAdj = 2; tbReNewAdj = 3; tbNewAdjAmt = 32; tbReNewAdjAmt = 48.
It turns out that unless, in this case, the text box format property is explicitly set to General Number that the data type is treated like "String" and the effects of using the "+" is like having used "&" to concatenate the strings.