Error in requested events

Hi everyone! I am facing problem with requested events. I am sharing picture, if anyone can help me. I have 30000 events , after appling cuts it gives error.

Maybe @moneta can take a look?

The message I think is clear. You are requesting more events for training (or testing) that are available in your input data set. You should decrease it or let TMVA select automatically according to the proportion you provide.
See the TMVA users guide par. 3.1.4 and table 2 for the various options.