The point on the floating rate index curve.
M = combination of a number between 1-12 and an "M" for month, e.g. 3M
Y = combination of number between 1-100 and a "Y" for year, e.g. 10Y
10Y-OLD = see above, then add "-OLD" when appropriate
INTERPOLATED = the point is mathematically derived
2/2031 5 3/8 = the point is stated via a combination of maturity month / year and coupon.