ASP.Net Core MVC [key] attribute field autoincrements improperly in database

Question

I have a [key] attribute property "txn_id" which is a primary key in my DB. When I first run my server and do some action which fills DB, txn_id autoincrements properly. Now, I run my server second time, do action which fills DB and see that txn_id is now autoincremented improperly ( it was 4 first time, second time it is 1004). How can I fix this? Image

Property:

[Key]
public int txn_id { get; set; }

Startup.cs:

 public class Startup
{
    public Startup(IHostingEnvironment env)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
            .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
            .AddEnvironmentVariables();
        Configuration = builder.Build();
    }

    public IConfigurationRoot Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        // Add framework services.
        services.AddDbContext<DataContext>(options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
        services.AddMvc();
        services.AddDistributedMemoryCache();
        services.AddSession(options =>
        {
            options.IdleTimeout = TimeSpan.FromSeconds(10);
            options.CookieHttpOnly = true;
        });
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory,DataContext context)
    {
        app.UseSession();
        loggerFactory.AddConsole(Configuration.GetSection("Logging"));
        loggerFactory.AddDebug();

        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseBrowserLink();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
        }

        app.UseStaticFiles();

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });
        context.Database.EnsureCreated();
    }
}