Lock(seconds) converts to a TimeSpan that is immediately converted to Milliseconds.

[AnthonyVO]

Looking at the reference source for Monitor.Try() you can see that internally it uses milliseconds and that it converts a TimeSpan to Milliseconds.

Therefore the Lock() overload that creates a TimeSpan from the seconds parameter causes a bunch of wasted cycles as it creates a timespan that is immediately converted to milliseconds.

https://referencesource.microsoft.com/#mscorlib/system/threading/monitor.cs