[Wien] Questions about the difference charge density in the Ti core

[Ding Peng]

Dear Wien2k experts,

I'm reading the latest publication for Wien2k (P. Blaha, K.Schwarz, F. Tran, R. Laskowski, G.K.H. Madsen and L.D. Marks, J. Chem. Phys. 152, 074101 (2020)) and confused about the figure showing the difference charge density of TiCoSb (Figure 9 in the paper). I noticed that the core charge densities for Ti and Co are very positive and the ones for Sb are very negative. To my best knowledge, Ti in TiCoSb is thought to have the chemical valence of +4, which means it tends to lose the electrons. However, this looks to contradict to the this graph, in which the difference charge densities in Ti are positive. So can someone explain why the difference charge densities in Ti core are very positive?

Sorry for asking this question that may look stupid.

Many thanks,
Ding