APT-pinning + Difference Pin: release a=* to Pin: release *?

Hi!

What is the difference from a file I have created
in "/etc/apt/preferences.d/"

Example file "snap-blocker" to exclude snapd packages on updates/upgrades.

Package: snapd
Pin: release *
Pin-Priority: -1

Package: snapd
Pin: release a=*
Pin-Priority: -10

?
Pin: release *
Pin: release a=*
?

Pin-Priority: -1 (-1 equals to ignore)
Pin-Priority: -10 (-10) ???

Difference of it?