applicable credit actually applied on f709 Schedule B column C

[gr3849]

I am working on my form 709 and do not know where I can find the right number to put in the Schedule B column C for gifts reported in prior years. The instruction says enter the applicable credit actually applied. What does it mean and where it come from in f709s? My prior year gifts are less than $500K. Thanks

[gr3849]

Can any expert please help with my questions?

Thanks