To address your question, you can make the following changes in the code:

1. Assign your extracted values in one variable

ans = df.iloc[:,0].str.extract(r'^(.?)\s(\d.?\d*)?$') # '\d+.\d+'

2. Access only first index only

ans[1]

Please refer to the image below for additional clarification.

https://i.sstatic.net/Qs9JGpfn.png