Cannot use save pages beyond slot 99

[seedship]

When I save to slot 99, it allows me to see that there are more save slots, but it won't let me use them

[CraigStern]

Hey seedship! That's a bug--there aren't any usable save slots past 99.

[verifiablesuspenders]

When I save to slot 99, it allows me to see that there are more save slots, but it won't let me use them

Is there any mistake? There is no backup box after box 99