How have courts interpreted reservation terms in a contract for giving time?

In Bailey v. Edwards, the reservation was in clear terms and need not be reproduced here because of its length. (For a further reservation, see Price v. Barker, supra). As was stated by Backburn J. [at p 774] it can be said that where there is a contract for giving time and there is an unqualified reservation of rights against the surety, the contract is to be construed as allowing the surety to retain all his remedies against the principal debtor and "'that the covenant not to sue is to operate only so far as the rights of the surety may be affected'".