С# Dapper Mapping Error

In my asp.net project I use dapper for getting data from an Oracle database. I have an sql request like this:

select SUM(( pt.end_date - pt.start_date ) * 24 ) time_coacsh                                           
      ,SUM(( pt.end_date - pt.start_date ) * 24 )/COUNT(rc.reg_coach_id) oborot_coacsh 
from ...

and a model with only these properties:

[Column("time_coacsh")]
public Double TimeCoacsh { get; set; }

[Column("oborot_coacsh")]
public Double OborotCoacsh { get; set; }

I am trying to get a list of objects through the following method:

public IEnumerable<TModel> Query<TModel>(string sql, object paramsSql = null)
{
    SqlMapper.SetTypeMap(typeof(TModel), new CustomPropertyTypeMap(typeof(TModel), BaseParamMappings.SelectProperty));

    return SqlMapper.Query<TModel>(_db, new CommandDefinition(sql, paramsSql, null, null, CommandType.Text)).ToList();
}

However I get this error:

Error parsing column 0 (TIME_COACSH=null)

If I execute the sql request in oracle I will get needed data without some null values.

In the model I tried to use Float, Decimal, Double, but I get the same error.