I can’t replicate. Can you let me know the version of EE and of PHP you’re running?
And if you go directly to the database table that holds the duration value and copy that value- what’s in the database?
On current versions of EE, that table will be exp_channel_data_field_x where x is the field id number.
And is it all entries with that field having an issue or just that particular one?
Ah- that really looks like a bug to me- it shouldn’t allow values that can’t be parsed into a duration to be saved.
I’ve dropped it in as a github issue and accepted it as a bug: https://github.com/ExpressionEngine/ExpressionEngine/issues/460
For the short term, it should be fine just to manually alter and resave the entry if anyone runs into this. Long term, validation needs a tweak.