What are you changing it from? If it's a Basic card, it may have html tags around it (eg <p>.25</p>).
Yes, Wagn should strip that when you change it to a number, but alas, it does not yet.
Workaround is to change to a phrase or plaintext first, clean the data, and then change to a number.
--Ethan McCutchen.....2018-03-01 19:24:40 UTC