canon - Is Sigma 150-600mm f 5-6.3 contemporary "F4-5.6" on Crop Sensor?

I bought Sigma 150-600mm f5-6.3 Contemporary DG OS HSM Lens for my Crop Sensor Canon 1300D.

What I've noticed is that it gives me max aperture of f5.6 at 600MM instead of f6.3 and f4.5 at 150mm on my Canon 1300D.

Please provide your views. Here's the link to the pic with Metadata–

Test Shot at 600MM f5.6