It's not unusual for transmissions to leak after sitting for extended periods. The oil from the torque converter will seep into the trans find a way to leak out. It's usually the front pump seal if it's leaking in the area you indicated. Don't panic however, clean it up, drive it, and you may find it's OK.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine