Calculating NDVI-Analyzing Results

I would like to calculate the NDVI for an area to identify vegetation cover over a 32 year period using. However, I am having challenges with the calculations I have attempted with Raster Calculator. I am using images acquired from the USGS Earth Explorer for the years 1988, 2000, 2017, 2018 and 2020. I have created the Multi Band Composites for each year and used the Bands from those Composite images to perform the calculation for NDVI in Raster Calculator.

For the first image 1988 (Landsat 4) I used Band 4 (NIR) and Band 3 (Red), using the equation

Float("1988compo_1988 – Band_4" – "1988compo_1988 – Band_3") / Float("1988compo_1988 – Band_4" + "1988compo_1988 – Band_3")

However, the results (seen in the screenshot below) were not what I was expecting, I.E values ranging from -1 – 1.

Is there a way I can get the values that are usually associated with NDVI? If not, how can I use these results to identify which areas are vegetation or not?